Preheat oven to 350°F/180°C. Line a mini muffin pan with paper liners. Set aside.
Melt butter in a medium saucepan. Remove from heat and add in chocolate and salt. Whisk until melted and smooth (if it doesn’t completely melt, cook on low heat for a few more seconds). Transfer to a large bowl. Add sugar and whisk until well combined. Add eggs and whisk until combined and shiny. Add flour and cocoa powder and, using a rubber spatula, fold just until combined and no more flour is visible.
Using a spoon or a piping bag, scoop or pipe the batter into the muffin pan, filling the tins almost all the way full. Bake until a toothpick inserted into the center of the brownies comes out with moist crumbs and not completely dry, 10-14 minutes. Allow brownies to cool in the pan for 10-15 minutes, then take them out of the tins and place them on a cooling rack, allowing to cool completely before serving.
Store brownie bites at room temperature in an airtight container for up to 2 days or in the refrigerator for up to 5 days. Brownies can be frozen for up to 2 months. Thaw on the counter, still covered, or overnight in the fridge.
