Preheat the oven to 350°F (175°C). Line a muffin tin with paper liners or lightly grease each cup to prevent sticking.

Mix the wet ingredients: In a large bowl, whisk together the melted butter and sugar until smooth. Add the eggs, one at a time, followed by the vanilla extract. Whisk until everything is fully combined and smooth.

Combine the dry ingredients: In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt. Sifting helps ensure there are no lumps and gives the brownies a smooth texture.

Add the dry ingredients to the wet ingredients: Gradually fold the dry ingredients into the wet mixture, stirring gently. Be careful not to overmix. Stir until just combined, and you’ll have a thick, luscious batter.

Fill the muffin tin: Divide the batter evenly among the muffin cups. You should fill each cup about 3/4 full. Use a spoon or an ice cream scoop for even portions.

Bake: Place the muffin tin in the preheated oven and bake for 18-22 minutes. The brownies should have a crackly top, and a toothpick inserted into the center should come out with a few moist crumbs.

Cool: Let the brownies cups cool in the tin for about 5 minutes, then transfer them to a wire rack to cool completely.