Dulce de Leche Buttercream
I'd like to make a true buttercream frosting. I usually make Rose's Mousseline Buttercream, and would prefer to base this frosting off of it.
The basic method is to whip a few egg whites to soft peaks, then stream in 248 degree sugar syrup, whip til cool, then add in a pound of softened butter a tablespoon at a time, then flavor. I'd prefer not to add all of the sugar syrup and then add more sweetness in the form of dulce de leche. Would I deflate the egg whites by adding the dulce in? Experience with this?
I've never done what you're describing exactly, but I've made caramel buttercream by making caramel and using it in place of the sugar syrup. I think that if you use dulce de leche that is heated, it should work. You may need to adjust both sweetness and fat content.
I'd happily remove some of the butter from this recipe! Do you think that heating the dulce de leche and adding it into the egg whites would kill the foam? My understanding was that the sugar syrup helps to stabilize the egg whites before any fat is added. I may be mistaken though.
TOTAL flop. The dulce de leche totally destroyed the egg white foam. I ended up doing a classic buttercream (egg yolks only), made my sugar syrup, when it had cooked, I added about the same amount of hot dulce de leche to it, and streamed the mixture into the yolks. I only used about half of it total. Then I added 3 sticks of butter and more dulce de leche. It was magnificent. Incredibly rich, but very tasty.
Lesson learned - don't add fat to egg whites until they are already set with softball-stage syrup.