Before starting this recipe, make sure you have frozen the candy bars or chopped candy bar pieces at least overnight.
Preheat your oven to 375°F if baking immediately. Line three cookie sheets with parchment paper or silicone mats. (See notes for suggestions if you do not own three.)
Sift or whisk the flour, baking powder, baking soda, and salt into a medium sized bowl.
2 cups (250 grams) all-purpose flour, ½ teaspoon baking powder, ½ teaspoon baking soda, 1 teaspoon salt
Add the brown sugar, granulated sugar, and softened butter to a mixing bowl or the bowl of your stand mixer beat together well.
¼ cup (50 grams or 1.8 ounces) granulated sugar, 1 cup (192 grams or 6.8 ounces) dark brown sugar, 1 cup (227 grams) unsalted butter
Add the eggs one at a time, then the vanilla, beating about one minute between each addition.
2 eggs, 2 teaspoons vanilla extract
Add the dry ingredients and mix only until just combined.
Chop the frozen candy bar pieces if you have not done it before freezing, then add the frozen candy bar pieces, reserving a tablespoon or so in case your last cookies are light or you want to add extra to the top, and mix by hand.
2 cups about (340 grams) chocolate-based candy bars
Use a #30 cookie scoop or two spoons to scoop two tablespoons of batter onto a baking sheet lined with parchment or silicone mat. If baking immediately, leave at least two inches between cookies. If scooping to freeze, they can be placed adjacent to each other but not touching. Freeze overnight before putting into a freezer bag and squeeze out all of the air.
Freeze the scooped cookie dough on the cookie sheet for 15 to 30 minutes. This reduces the cookie spread.
Bake one cookie sheet at a time at 375℉ for 10 to 12 minutes, until the edges are just starting to brown. The centers will still be soft.
Leave the baked candy bar cookies on the baking sheet for a few minutes until completely cool, then store in an airtight container at room temperature.