Once the brownies are completely cool, I make the mint frosting. In a mixing bowl, I beat the softened butter until it’s smooth. I gradually add the powdered sugar, milk, and peppermint extract, beating until it’s light and fluffy. If I’m using it, I add a drop or two of green food coloring. I spread this fluffy mint layer evenly over the cooled brownies. Then, for the ganache, I heat the cream until it’s just simmering, pour it over the chocolate chips in a bowl, let it sit for 3 minutes, then whisk until smooth. I let it cool for about 5 minutes to thicken slightly, then pour and spread it over the mint layer. I let the whole pan set at room temperature until the ganache is firm before slicing.
Pro Tips for Best Results
For the fudgiest brownies, don’t overbake them. The toothpick test should yield a few fudgy crumbs, not come out clean. A clean toothpick means they’re overdone. They will set up perfectly as they cool. I always set a timer for the minimum baking time and check from there.
Let every layer cool completely before adding the next. Rushing is the enemy of clean layers. Warm brownies melt the frosting, and warm frosting melts the ganache. I often make the brownies in the morning and finish the layers in the afternoon, or even spread the process over two days.
For a perfectly smooth ganache layer, let it cool and thicken slightly after whisking. Pour it into the center of the mint layer and gently guide it to the edges with an offset spatula. If it’s too runny, it will flood over the sides; if it’s too thick, it will be hard to spread. A 5-7 minute rest after whisking is usually perfect.
Common Mistakes to Avoid
My first batch had a weeping, greasy mint layer because I used butter that was too soft, almost melted, for the frosting. Your butter should be softened to room temperature—able to hold an indent when pressed but still cool and firm. This creates a stable, fluffy frosting that won’t separate or melt.(See the next page below to continue…)