in search of different buttercream recipes

I just made this recipe for a giant cupcake cake over the weekend…it held up great:
White Chocolate Buttercream
Ingredients
6oz white chocolate
1/4 cup heavy cream
1 cup butter, softened
2 lbs powdered sugar
Instructions
Microwave the white chocolate and cream for 1-1/2 mins, or til the chocolate is melted. Gradually add butter and powdered sugar until fluffy. Makes 3-1/2 cups

However, your ‘bulges’ may be from another source; make sure your let your layered cakes ‘rest’ with crumb icing prior to covering with the final buttercream and use the ‘dam’ method (a thick line of icing around edge before stacking). Hope this helps.