Preheat the oven to 350F. Butter the wells of a 24-cup mini-muffin pan or spray with baking spray.

In a medium saucepan, melt the butter over medium heat. Stir in the sugar, cocoa powder, vanilla, and salt. Remove from the heat and let cool for 5 minutes.

Quickly whisk in the eggs until well combined. Add the flour and stir until mostly combined, then add the chocolate chips and stir until no flour remains. Scoop the batter into the grease muffin tin.

Bake for 12 to 15 minutes or until the brownies are set and the tops or cracked and shiny. Let cool in the pan on a wire rack for 10 minutes. Using the tip of a knife, carefully remove the brownie bites from the pan and finish cooling on the wire rack. Store any leftovers in an airtight container at room temperature for up to 1 week or freeze for up to 2 months.