Cream together your butter and both sugars until it's light and fluffy.
Add in the egg and vanilla, mixing thoroughly.
In a separate bowl, whisk together the flour, baking soda, and salt. Add the flour mixture to the butter mixture and mix until combined.
When that is done, fold in the mint chocolate chips/bits by hand.
Place a sheet of parchment paper on a baking sheet.
Using a 1 1/2 tablespoon cookie scoop, place them onto the prepared baking sheet. About 8 per sheet.
Take a piece of wax paper or parchment paper and place it over the cookie. With a flat-bottomed glass, press the cookie flat. This is the only way they won't stick to the cup—trust me, it's a sticky dough. Flatten each of them as much as you can.
Bake at 375 degrees for 9-11 minutes, until golden brown.