Make the Cake Layers

1. Prepare three 8 inch cake pans with parchment paper circles in the bottom and grease the sides. Preheat oven to 350°F (176°C).
2. Combine the flour, baking powder and salt in a medium sized bowl and set aside.
3. Add the butter, sugars and vanilla extract to a large mixer bowl and beat together on medium speed until light in color and fluffy, about 2-3 minutes. Do not skimp on the creaming time.
4. Add the sour cream and mix until well combined.
5. Add the eggs one at a time, mixing until mostly combined after each. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
6. Add half of the dry ingredients to the batter and mix until mostly combined.
7. Slowly add the milk and mix until well combined.
8. Add the remaining dry ingredients and mix until well combined and smooth. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated. Do not over mix the batter.
9. Fold in the toffee bits.
10. Divide the batter evenly between the cakes pans and bake for 22-25 minutes, or until a toothpick comes out with a few crumbs.
11. Remove the cakes from the oven and allow to cool for about 2-3 minutes, then remove to cooling racks to cool completely.

Make the Toffee Sauce:

1. While the cakes cool, make the toffee sauce. Add the butter and brown sugar to a large saucepan and heat over medium heat (or medium-low, if your stove heats a little warmer than some) Melt the butter and allow the brown sugar to dissolve. Slowly bring the mixture to a boil. This should take about 10-15 minutes. Do not be tempted to turn the temperature higher to speed the process up. The sugar won’t dissolve properly and the toffee sauce could split. If the mixture begins to boil before the sugar is fully melted, turn the heat down.
2. When the sugar is melted and the mixture begins to boil, slowly pour in the cream whip whisking constantly. The mixture will bubble up. Continue whisking until everything comes together.
3. Slowly bring mixture back to a boil over medium-low heat. Boil until thick enough to coat the back of a spoon.
4. Remove sauce from heat and add vanilla extract and salt. Allow the sauce to cool to room temperature, then refrigerate until completely cooled.

Make the Buttercream:

1. When the cake and toffee sauce have cooled and you’re ready to build the cake, make the buttercream. Add the butter to a large mixing bowl and beat until smooth.
2. Slowly add half of the powdered sugar and mix until well combined and smooth.
3. Add half a cup of toffee sauce and the salt and mix until well combined.
4. Slowly add the remaining powdered sugar and mix until well combined and smooth. Add toffee sauce, as needed, to get the right consistency of frosting and flavor. You want the buttercream to be thick enough to hold the filling of the cake in place, but also not be too thick and have good flavor. See my post on frosting consistency for more information.

Build the Cake:

1. To put the cake together, use a large serrated knife to remove the domes from the top of the cakes so that they’re flat. These cakes don’t have a large dome, but I like to make sure they’re completely flat.
2. Place the first cake on a serving plate or a cardboard cake round.
3. Spread about 1/2 a cup of buttercream evenly on top of the cake.
4. Pipe a dam of buttercream around the outer edge of the cake, on top of the layer of buttercream you just added. Fill the dam with about 1/2 a cup of toffee sauce and spread evenly. You want the top of the dam to be even with the toffee sauce.
5. Add the second layer of cake and another layer of frosting, a dam and toffee sauce.
6. Top the cake with the remaining layer and frost the outside of the cake. Refer to my tutorial for frosting a smooth cake, if needed.
7. Gently warm the remaining toffee sauce in the microwave for about 10 seconds at a time, stirring between each 10 second increment. Don’t over-heat the sauce or it could separate. Use it to add a drip to the sides of the cake, if desired.
8. Finish off the cake with a rim of toffee pieces around the top and bottom of the cake.
9. Store cake in an air-tight container in the fridge. Serve at room temperature. Cake is best if eaten within 3-4 days.