Dave's comment on the buttercream was "I could brush my teeth with that." I'm guessing that's a compliment (but I really wouldn't recommend brushing your teeth with frosting!).
I got the cake recipe from Chockylit's now defunct blog (but she still has her recipes posted there) and it will now be my go-to recipe for chocolate cake. The only thing I did differently was I used a dark cocoa powder rather than a regular one because that's what I had on hand.
For the frosting recipe I used the same base I use when I make the salted caramel cupcakes, just substituting Dulce de Leche for the salted caramel.
The filling is homemade, recipe to follow - it's SUPER easy!
Preheat the oven to 425° F.
Pour one can (14 ounces) of sweetened condensed milk (not evaporated milk) into a glass pie plate or shallow baking dish. Stir in a few flecks of sea or kosher salt.
Set the pie plate within a larger pan, such as a roasting pan, and add hot water until it reaches halfway up the side of the pie plate.
Cover the pie plate snugly with aluminum foil and bake for 1 to 1¼ hours. (Check a few times during baking and add more water to the roasting pan as necessary).
Once the Dulce de Leche is nicely browned and caramelized, remove from the oven and let cool. Once cool, whisk until smooth.
Store in the refrigerator until ready to serve. Warm gently in a warm water bath or microwave oven before using.