Preheat the oven to 325 degrees F. Line baking sheets with parchment paper or silpat mats (or spray with nonstick spray).
In a large bowl, use an electric mixer to combine the butter and cream cheese. Mix in the sugar, then mix in flour and extract. Stir in 1 cup of the mint chunks.
Use a cookie scoop or a spoon to drop rounded tablespoonfuls of dough onto your prepared baking sheets about 2 inches apart. Top each round of dough with a few additional pieces of mint. Bake 20 minutes, or until golden and set. Remove to a wire rack and sprinkle with powdered sugar. Cool completely.
Notes
For the recipe pictured, I used Guittard Mint Chips, but you can also use Andes Peppermint Crunch thins (chopped) or something similar or any kind of white mint chip.