Butterscotch and dark chocolate, a perfect pair!
Preheat oven to 350F. Line a cookie sheet with parchment paper.
Stir all dry ingredients together in a bowl. Add butter, egg, and egg yolk, and stir until combined.
Stir in 1/4 cup of the butterscotch chips, and all of the milk chocolate chips.
Place 1.5-inch balls of dough at least 2 inches apart on cookie sheet. Use fingers to smooth out each dough ball, then press each ball down slightly.
Use the remaining 1/4 cup of the butterscotch chips to generously top each cookie.
Bake for 7-10 minutes. Allow to cool, and enjoy!