Preheat the oven to 350ºF. Line baking sheets with parchment paper and set aside.
Chop the 8 Fun-size Milky Way candy bars into small pieces, spread them in a single layer on a plate or sheet, and freeze until firm.
In a large bowl, cream 1 cup butter (room temperature) with 3/4 cup light brown sugar, 1/4 cup dark brown sugar, and 1/2 cup sugar until light and fluffy.
Add 2 eggs and 1 tablespoon vanilla to the creamed mixture and beat until combined.
In a separate bowl, whisk together 2 3/4 cups flour, 1/2 teaspoon baking soda, 1/2 teaspoon baking powder, and 1/2 teaspoon salt.
Gradually add the dry ingredients to the wet ingredients and mix just until combined and no dry streaks remain.
Fold in 12 ounces mini semi-sweet chocolate chips (or regular chips) and the frozen chopped Milky Way pieces until evenly distributed. Fold gently so the Milky Way pieces remain cold.
Use a rounded tablespoon to portion dough onto the prepared baking sheets, spacing cookies about 2 inches apart.
Bake at 350ºF for 8–10 minutes for rounded tablespoon-sized cookies, until edges are set (centers may still be soft).
Immediately after removing the cookies from the oven, if caramel has oozed out and pooled around a cookie, use a sharp knife to scrape excess caramel away from the cookie before it cools and hardens.
Let cookies cool on the baking sheet for a few minutes, then transfer to a wire rack to finish cooling.