Butter and line with parchment paper a 9” x 9” brownie pan. You’ll want to leave a 2” overhang of parchment paper to allow for easy removal of the fudge.
In a medium saucepan over medium-low heat, combine the milk chocolate chips, condensed milk, and butter. Stir often as to prevent the chocolate from scorching, until it is all completely melted. Be careful to keep the heat near or below medium, as having too high of heat can burn the chocolate.
Remove the saucepan from the stove and whisk in the vanilla and peppermint extracts. Pour the fudge into the pan, and let sit for at least three hours, until solid.
Once the fudge has set, melt the white chocolate in the microwave (about 1 minute on high combined with a vigorous stirring should do) and whisk in the matcha powder. Evenly pour it over the fudge, and smooth out with a spatula or knife. Let sit for at least another hour, until firm. Decorate with extra melted white chocolate drizzles, if desired.
Remove the fudge from the pan by lifting up on the parchment paper. Cut it into 12 – 16 cubes, and serve. The fudge can be stored in the fridge in an air tight container for up to five days.