Preheat your oven to 350°F (175°C). Lightly coat a mini muffin tin with oil, or use paper liners to keep things mess-free.

Melt the butter in a microwave-safe bowl or saucepan, then mix in the cocoa powder until smooth and well combined. Let it cool slightly.

In a large bowl, whisk together the sugar, eggs (or flax eggs), and vanilla extract until well combined.

Gradually pour the cocoa-butter mixture into the sugar mixture, stirring constantly to keep everything well blended. Gently fold in the sifted flour, baking powder, and salt until everything is just mixed. Avoid overmixing.

If you're adding chocolate chips, gently fold them into the batter.

Use a cookie scoop or spoon to fill each mini muffin cavity about three-quarters full.

Pop the muffin tin into the oven and bake for 12-15 minutes. To check if they're done, insert a toothpick in the center—if it comes out with a few moist crumbs but no wet batter, they're ready!

Let the brownie bites sit in the tin for around 5 minutes, then gently transfer them to a wire rack to cool off completely.