01 - Preheat oven to 350°F. Line a mini muffin tin with paper liners or grease thoroughly.
02 - Whisk melted butter and granulated sugar in a large mixing bowl until homogeneous.
03 - Add eggs and vanilla extract to the mixture. Whisk until smooth and glossy.
04 - Sift cocoa powder, all-purpose flour, salt, and baking powder over the wet ingredients. Stir gently until just combined; avoid overmixing.
05 - Spoon 1 tablespoon of batter into each mini muffin cup.
06 - Place approximately 1 teaspoon Nutella atop each batter portion and use a toothpick to create a swirl.
07 - Gently press one small salted pretzel into the top of each filled cup.
08 - Bake for 13 to 15 minutes or until the edges are set and a toothpick inserted yields a few moist crumbs.
09 - Cool bites in the muffin tin for 10 minutes, then transfer to a wire rack to finish cooling completely.