Peanut Butter–Candy Bar Thumbprint Cookies

1. Preheat oven to 375°F. Line 2 baking sheets with parchment paper. Whisk together flour, baking soda, baking powder, and salt in a bowl. 

2. Beat butter, peanut butter, granulated sugar, and brown sugar with an electric mixer on medium speed until light and creamy, 1 to 2 minutes. Add egg and vanilla; beat until combined. Reduce the mixer speed to low and gradually beat in flour mixture just until combined, scraping bowl to incorporate if needed.

3. Place sanding sugar in a bowl. Scoop dough into 40 balls using a 1 tablespoon cookie scoop. Roll each ball in sanding sugar and place 2 inches apart on prepared baking sheets. Press thumb gently into center of each cookie to indent.

4. Bake, in batches, until bottoms are lightly browned, 8 to 10 minutes. Immediately press one candy bar into center of each cookie. Cool on baking sheets on a wire rack, 10 minutes. Transfer cookies to wire racks to cool completely.