Preheat your oven to 350℉ (180℃). Line 12 muffin cups with liners and set them aside.
In a medium heatproof bowl, place your chocolate and butter. Heat the mixture in the microwave in 20-second intervals, stirring between each interval, until fully melted. Set the bowl aside to cool slightly.
In a small bowl, sift together the flour, cocoa powder, and salt. Set the dry mixture aside for later use.
Using an electric mixer, whisk the eggs and sugar on high speed until thick and pale (about 4 minutes). Reduce speed to low and blend in the melted chocolate mixture.
Add the sifted flour mixture to the wet ingredients. Gently fold the dry ingredients into the wet mixture just until combined.
Divide the brownie batter evenly among the prepared muffin cups, filling each about ¾ full. Bake for 13-15 minutes or until a toothpick comes out with moist crumbs.
After baking, transfer the brownie muffins to a wire rack and let them cool for at least 10 minutes before removing them from the pan.
