Preheat oven to 350 degrees F. Grease or spray top of a 12 cup muffin pan with cooking spray and line cups with paper liners.

Place butter in a 2 cup glass measuring cup; microwave on high for one minute or until butter melts. Add cocoa to melted butter and stir well. Set aside and let cool slightly.

Whisk eggs, sugar, vanilla and salt together in a medium mixing bowl. Add butter/cocoa mixture and stir until well mixed. Add flour, stirring just until blended’ stir in ⅓ cup of the chocolate chips.

Spoon the muffin batter into cups, dividing evenly among all 12 (halfway full).

Stir together remaining ⅓ cup chocolate chips, toasted pecans and mini marshmallows. Set aside.

Bake muffins for 18 minutes. Pull pan from oven and sprinkle with marshmallow mixture. Return to oven and bake for 2 minutes more for a total bake time of 20 minutes. Let cool in muffin tins for about 10 minutes, then carefully loosen muffins from tins and let cool completely before serving.

Note: If you skip the topping, divide batter among 10 muffins cups to make the brownie muffins slightly taller. Bake time is still 20 minutes.