Combine the flour, sugar, cocoa powder, baking powder, baking soda, and salt in a mixing bowl.
In another mixing bowl, combine the butter, milk, eggs, and vanilla. Whisk until fully incorporated.
Slowly mix the dry ingredients into the wet ingredients without over beating.
Once the batter is smooth and incorporated fully, gently fold in 1 cup of chocolate chips.
Spray the jumbo muffin liners with oil and place them in the air fryer basket. Scoop in the batter to fill ¾ full. Top with more chocolate chips and sprinkle with coarse sugar.
Cook at 375°F for 4 minutes, then drop heat to 325°F for 11 minutes or until the center of the muffins is cooked.
Let rest and cool before removing from liners.
Notes
Be careful not to overmix the batter after adding the dry ingredients to the wet. Overmixing can lead to dense muffins rather than light and fluffy ones.Air fryer models can vary, so keep an eye on the muffins as they cook. If they brown too quickly, you can lower the temperature slightly.To test for doneness, insert a toothpick into the center of a muffin. If it comes out with a few moist crumbs (but not wet batter), the muffins are done.