I rarely flavor my Italian butter cream other than vanilla. My son asked for mint, white chocolate and vanilla for his birthday cake this year. Decorations will be white chocolate since he hates fondant, cake is vanilla. I want to add mint extract to my frosting recipe which I use Cake love's if that helps. Not sure how much to start with for a hint of mint. Trying not to make it over powering. The extract box suggests quarter teaspoon for frosting

Mint is suck a strong flavor I think I’d start with only 1/8th teaspoon.   You can always add more if necessary but it’s impossible to correct if you get too much. 

Kakeladi, that's what I was thinking less is better. Am rushing this cake as his birthday dinner got pushed up two days. Besides using a new pan shape and new flavor in the icing,the design is a lot of pieces of chocolate.