For the Apple Cake:

• 3 cups all-purpose flour, divided
• 2 teaspoon baking powder
• 1 teaspoon cinnamon
• ½ teaspoon salt
• 1 cup unsalted butter, softened
• 2 cups granulated sugar
• 2 teaspoons vanilla extract
• 4 large eggs
• 1 cup whole milk
• 3 cups apples (peeled and diced into ½ inch cubes or smaller) – a mix of sweet and tart is recommended
• ½ cup chopped pecans

For the Pecan Crunch:

• ½ cup quick cooking oats
• ¼ cup chopped pecans
• ¼ cup brown sugar
• ¼ cup all-purpose flour
• 3 tablespoons unsalted butter, softened
• 2 tablespoons honey
• pinch salt

For the Cinnamon Buttercream:

• 6 large egg whites
• 2 cups granulated sugar
• 3 cups unsalted butter, softened
• 2 teaspoon vanilla extract
• ¾ teaspoon cinnamon, or to taste

For the Toffee Sauce:

• 6 tablespoons unsalted butter
• ¾ cup brown sugar
• 1 tablespoon dark corn syrup (light corn syrup will also work)
• ⅓ cup heavy cream
• 1 teaspoon vanilla extract
• 2 teaspoons scotch or bourbon (optional, for added depth of flavor)
• large pinch salt

For the Assembly:

• Chopped pecans or reserved pecan crunch
• Toffee buttercream (made by mixing extra sauce with remaining buttercream, as detailed below)

Step-by-Step Instructions to Create Your Apple Toffee Crunch Cake

To Make the Apple Cake:

1. Pre-heat your oven to 350 degrees Fahrenheit (175°C). Lightly grease the bottoms of two 8-inch round cake pans. Line the bottoms with parchment paper, then grease and flour both the parchment and the sides of the pans. Set them aside.
2. Measure out 1/3 cup of the all-purpose flour and set it aside separately for later use.
3. In a medium bowl, sift together the remaining flour, baking powder, cinnamon, and salt. This ensures all dry ingredients are evenly distributed. Set this mixture aside.
4. In the bowl of an electric mixer fitted with the paddle attachment, beat the softened unsalted butter until it is smooth and creamy. Gradually add the granulated sugar. Continue to cream the sugar and butter together on medium speed until the mixture becomes light, fluffy, and pale in color. Incorporate the vanilla extract.
5. Reduce the mixer speed to medium-low. Add the eggs one at a time, allowing each egg to fully incorporate before adding the next. Stop the mixer occasionally and use a rubber spatula to scrape down the sides of the bowl, ensuring everything is well combined.
6. With the mixer still on low speed, add half of the sifted dry ingredients to the butter mixture, mixing until just combined. Follow this with the whole milk, mixing until just incorporated. Finally, add the second half of the dry ingredients and mix only until combined, being careful not to overmix, which can result in a tough cake.
7. Toss the diced apples with the 1/3 cup of reserved flour. This step helps prevent the apples from sinking to the bottom of the cake. Gently fold the floured apples and chopped pecans into the cake batter until they are evenly distributed throughout.
8. Divide the prepared batter evenly between the two 8-inch cake pans. Bake for 32 to 35 minutes, or until the tops are golden brown and a thin knife or wooden skewer inserted into the center of the cakes comes out clean. Allow the cakes to cool on a wire rack for 15 to 20 minutes before carefully removing them from their pans to cool completely.

To Make the Pecan Crunch:

1. Increase your oven temperature to 375 degrees Fahrenheit (190°C). Line a baking sheet with parchment paper or a silicone baking mat and set it aside.
2. In a medium bowl, combine all of the ingredients for the pecan crunch: quick cooking oats, chopped pecans, brown sugar, all-purpose flour, softened unsalted butter, honey, and a pinch of salt. Stir everything together thoroughly with a wooden spoon until well combined and crumbly.
3. Spread the pecan crunch mixture out evenly onto the prepared baking pan. Bake for 8 to 10 minutes, making sure to stir the crumbles halfway through, until they are golden brown and fragrant. Let the pecan crunch cool completely on the baking sheet; it will crisp up as it cools. Once cooled, break it into small, bite-sized pieces before using.

To Make the Cinnamon Buttercream:

1. Place the egg whites and granulated sugar into the bowl of an electric mixer (or a heatproof bowl if using a hand mixer). Whisk them briefly by hand until they are just combined.
2. Fill a saucepan with a few inches of water and bring it to a gentle simmer over medium heat. Place the mixer bowl directly on top of the saucepan, creating a double-boiler setup. Ensure the bottom of the bowl does not touch the simmering water.
3. Whisking constantly to prevent the eggs from scrambling, heat the egg mixture until it registers 160 degrees Fahrenheit (71°C) on a candy thermometer. Once the mixture reaches the correct temperature, carefully remove the mixer bowl from the saucepan and return it to the stand mixer.
4. Using the whisk attachment, whip the egg white mixture on high speed for 8 to 10 minutes. Continue whipping until the bowl is no longer warm to the touch and the meringue is fluffy, glossy, and holds stiff, firm peaks.
5. Stop the mixer and switch out the whisk attachment for the paddle attachment.
6. With the mixer on low speed, gradually add in the vanilla extract, cinnamon, and the softened butter, a couple of tablespoons at a time, allowing each addition to incorporate before adding more.
7. Once all of the butter has been added, increase the mixer speed to medium-high and continue to mix until the buttercream is silky smooth and light. NOTE: If the mixture appears curdled or separated, do not despair! Just keep mixing; it can take up to about 5 minutes for it to come together and become smooth. If, on the other hand, it appears too soupy or thin, place the mixer bowl in the refrigerator for 10 to 15 minutes to firm up slightly, then continue mixing until smooth and emulsified.

To Make the Toffee Sauce:

1. In a medium saucepan, melt the unsalted butter over medium heat. Once completely melted, stir in the brown sugar and dark corn syrup. Increase the heat to high. While continuously stirring with a wooden spoon, bring the mixture to a rolling boil and cook for approximately 5 minutes, or until the sugar has fully dissolved and the sauce begins to thicken slightly.
2. Remove the saucepan from the heat. Carefully and slowly whisk in the heavy cream. Reduce the heat on the stovetop to low. Return the saucepan to the stove and whisk slowly but constantly, allowing the sauce to simmer gently for about 8 minutes.
3. Remove the saucepan from the heat once more. Stir in the remaining ingredients: vanilla extract, scotch or bourbon (if using), and a large pinch of salt. Pour the finished toffee sauce into a heat-safe container and allow it to cool and thicken to a pourable consistency.

To Assemble the Apple Toffee Crunch Cake:

1. Once your apple cake layers have completely cooled, carefully use a long serrated knife to slice each 8-inch cake in half horizontally, creating a total of four layers. Place one of the bottom cake layers on a cake board or your desired cake pedestal. Spread about 1 cup of the cinnamon buttercream evenly over this layer, then generously sprinkle with ½ cup of the prepared pecan crunch. Top with the next cake layer and repeat this process until all four cake layers are stacked with buttercream and crunch in between. Frost the entire stacked cake smoothly with the remaining cinnamon buttercream. Transfer the cake to the refrigerator to chill for 15 to 20 minutes; this helps set the buttercream and makes the toffee drip easier to control.
2. After the toffee sauce has cooled sufficiently but is still beautifully liquidy and pourable, carefully drip the sauce around the edges of the chilled cake, allowing it to slowly cascade down the sides for a beautiful visual effect. Once the edges are done, pour any remaining toffee sauce into the center of the cake top and use a small offset spatula to gently smooth it out. Be mindful that this toffee sauce is naturally a bit thicker than regular caramel, so exercise caution not to drag or mix it with the buttercream underneath when spreading it across the top.
3. To create a special toffee buttercream, take any remaining cinnamon buttercream and mix in a couple of tablespoons of the leftover toffee sauce, or adjust to your taste. This creates a rich, nuanced frosting. Using an open star tip, pipe decorative swirls or borders on top of the cake. Finally, sprinkle generously with additional chopped pecans or more of the leftover pecan crunch for a finishing touch and extra texture. Your glorious Apple Toffee Crunch Cake is now ready to impress!

• If your toffee sauce cools too much and becomes too firm to pour, simply re-heat it gently in the microwave in 10-second intervals, stirring in between, until it reaches a pourable consistency once again. Be careful not to overheat.
• Ensure the pecan crumbles are broken into relatively small pieces before incorporating them into the cake layers. Larger pieces can make the cake challenging to slice cleanly.
• For optimal freshness and to maintain its structure, store the assembled Apple Toffee Crunch Cake in the refrigerator. However, for the very best flavor and texture experience, always remember to bring it to room temperature before serving. The flavors truly blossom and the buttercream softens beautifully when not chilled.
• Once the cake is assembled and thoroughly chilled, the toffee sauce, while still delicious, may lose some of its initial glossy sheen. This is a natural characteristic of a brown sugar-based toffee.
• For variations, you can choose to keep this recipe as a simpler two-layer cake instead of four. Alternatively, if you prefer slightly thinner layers or have specific pan sizes, you can bake the batter in three 8-inch pans. If adjusting the number of layers or pan sizes, be sure to adjust the baking time accordingly; three thinner layers will bake faster than two thicker ones.