butter, unsalted, soft but cool, cut into small pieces
pure vanilla extract
plus 2 tablespoons of the caramel sauce
1In a medium , heavy bottomed saucepan, whisk the sugar and flour together.
2Add the milk and cream and cook over medium heat, whisking occasionally, until the mixture comes to a boil and has thickened, about 10-15 minutes.
3Transfer the mixture to the bowl of a standing mixer fitted with the paddle attachment.
4Beat on high speed until cool. Reduce the speed to low and add the butter and vanilla, mix until thoroughly incorporated.
5Increase the speed to medium and beat until the frosting is light and fluffy. Add 1/3 cup of the caramel and continue mixing until combined.
6If the frosting is too soft, put the bowl in the refrigerator to chill slightly, then beat it again until it is the proper consistency.
7If the frosting is too firm, set the bowl over the pot of simmering water and beat with a wooden spoon until it is the proper consistency.
8Assembly of the cake: Place one of the cake layers on the cake base and level of the top.
9Put a thin layer of caramel sauce on the layers and then spread caramel buttercream on top. Next, add another layer of cake and level and frost as you did with the first layer.
10Trim the top of the last layer and then place it on the top of the cake bottom side up.
11Spread a very thin layer of frosting over the entire cake (crumb coat) and place the cake in the fridge for 30 minutes.
12Remove the cake from the fridge and use the remaining frosting to ice the top and sides.
13Use the remaining caramel to drizzle over the top. Add chopped nuts, if desired.