Preheat the oven to 425°F. Line a standard 12-cup muffin tin with paper liners and lightly spray the liners with nonstick baking spray.
In a large bowl, use a fork to mash the bananas. Some chunks are okay.
Add the slightly cooled melted butter, granulated sugar, egg, and vanilla extract. Whisk together until fully combined.
In a separate medium bowl, whisk together the flour, cocoa powder, baking soda, baking powder, and salt.
Add the dry ingredients to the banana mixture. Use a rubber spatula to gently fold everything together until just combined. Do not overmix.
Fold in the chocolate chips and freeze-dried strawberries.
Divide the batter evenly between the 12 muffin cups, filling each cup almost to the top (about ¾ full).
Press a few extra chocolate chips and freshly diced strawberries on top of each muffin.
Bake at 425°F for 5 minutes.
Without opening the oven door, reduce the oven temperature to 350°F and continue baking for 10 to 12 minutes, or until the muffin tops are set and spring back lightly when touched. A toothpick inserted into the center should come out with a few moist crumbs, but no wet batter.
Let muffins cool in the tin for 5 minutes before transferring to a wire rack to cool completely.