I have a great kumquat-flavored simple syrup that I'd like to make into a simple icing for a cake. I have butter but I want to know if there's any tried & true way to use simple syrup to make icing.
A seven minute frosting which is like a swiss meringue buttercream. Instead of making the simple syrup just heat and use your kumquat syrup here is a link to Martha Stewarts recipe. I think it would be delicious!
It doesn't use any butter so it differs from a traditional buttercream icing but its very light and fluffy and I imagine with the syrup you have it would be really nice.
The Williams Sonoma Cakes cookbook has a really nice buttercream recipe using simple syrup. It seems like you could use your kumquat flavoured simple syrup for this. Here's a recipe: http://www.thebakingpan.com/recipes/frosting/classic-french-buttercream.html