MAKES ABOUT 2 CUPS A subtle mint finish rounds out this luscious frosting, which can be refrigerated for up to 5 days; bring it back to room temperature before using.
1/4cupfresh mint leaveschopped
1cup(6 ounces) semisweet chocolate chips
1/3cupfirmly packed light brown sugar
16tablespoons(8 ounces/2 sticks) unsalted butter, very soft
3/4teaspoonpure vanilla extract
1/4teaspoonfine sea salt
In a saucepan, bring the milk to a boil, add the mint, then turn off the heat and let rest for 15 minutes.
Strain the milk, pressing the mint to release all the flavor. Let cool completely.
Over a double boiler on medium heat, melt the chocolate chips with the brown sugar and cocoa powder, stirring occasionally, until smooth and combined with no residual sugar grit, 10 to 15 minutes. Let cool.
In a stand mixer fitted with the paddle attachment, cream the butter with the vanilla, powdered sugar, and salt on medium-high speed until light and fluffy, 3 to 4 minutes. Add the cooled chocolate mixture and beat again for 2 minutes. Scrape down the bowl and mix again until combined. Add the cooled, mint-infused milk, mixing until fully incorporated.