In the bowl of a stand mixer, mix the butter with the sugars on medium speed for about 2 minutes until lighter in texture.
Add the egg and vanilla and continue to mix for about 30 seconds until combined.
Add the flour, baking soda, and salt and mix on low until just combined.
Using a spatula, fold in the chopped peppermint bark.
Cover the bowl and chill in the refrigerator for 30 minutes.
Line two baking sheets with parchment paper and preheat the oven to 350 Degrees F.
Using a medium 2 tablespoon cookie scoop, transfer scoops of the dough onto the prepared baking sheets leaving about 3 inches between them to allow space for them to spread.
Bake in the oven for 12-14 minutes until they are lightly browned and the edges have crisped up. They should still appear quite soft in the center.
Out of the oven, place the mouth of a drinking glass over each cookie and swirl it around the make them perfect circles.
Let the cookies cool on the baking sheet for 10 minutes before transferring to a baking rack to finish cooling.
Serve, or freeze for later. Cookies will keep wrapped tightly at room temperature for up to 5 days.