Black Walnut Frosting

Step 1
Combine egg whites, sugar, water, and cream of tartar in in the top of a double boiler over simmering water. Beat at low speed until mixture reaches 140 degrees F (60 degrees C). Do not stop beating while checking temperature, otherwise egg whites will overcook. Beat on high speed until mixture reaches 160 degrees F (71 degrees C), 2 to 4 minutes.

Step 2
Remove bowl from heat and stir in vanilla and black walnut extracts. Beat egg whites to cool on high speed, 3 to 5 minutes.

Step 3
Place a large dollop of the beaten egg white mixture in a separate bowl. Add butter and beat until well combined. Continue beating in dollops of egg white mixture until all egg white is incorporated and frosting is smooth and fluffy. Use to frost any cake; garnish with black walnuts.