01 - Preheat oven to 350°F. Line a mini muffin tin with paper liners or grease thoroughly.
02 - In a large mixing bowl, whisk the melted butter and granulated sugar until fully blended.
03 - Add eggs and vanilla extract, whisk until mixture is smooth and glossy.
04 - Sift in cocoa powder, all-purpose flour, salt, and baking powder. Stir gently just until blended; avoid overmixing.
05 - Spoon approximately 1 tablespoon of batter into each compartment of the prepared muffin tin.
06 - Add about 1 teaspoon chocolate-hazelnut spread on top of each batter portion. Use a toothpick or skewer to lightly swirl the topping into the batter.
07 - Gently press one small salted pretzel into the top of each portion.
08 - Bake for 13 to 15 minutes until edges are set and a toothpick inserted in the center removes with a few moist crumbs.
09 - Leave brownie bites to cool in the tin for 10 minutes before transferring to a wire rack to cool completely.