Step 1

Line about 8 silicone muffin cups with paper liners and set aside.

Step 2

Preheat the air fryer to 400°F (204°C).

Step 3

In a large bowl, whisk together the flour, baking powder, baking soda, and salt and set aside.

Step 4

In another large mixing bowl, whisk together the butter and oil until combined. Then whisk in the egg to combine. Add the buttermilk, sour cream, and vanilla and stir to combine. Whisk in the sugar until well combined for about 1 minute. Add the flour mixture and whisk just to combine. Fold in the banana chunks, chocolate chips, or blueberries, if you like.

Step 5

Spoon the batter into the prepared silicone cups until almost full. Top with coarse sugar or streusel topping if desired.

Step 6

Bake at 400°F (204°C) for 4 minutes. Then, leaving the air fryer basket closed, lower the heat to 325°F (163°C) and bake for another 11 to 13 minutes, or until a toothpick inserted into the center of a muffin comes out clean.

Step 7

Remove from the oven and let cool in the silicone cups for 5 minutes. Then transfer to a wire rack and let cool completely before serving. Store in an airtight container at room temperature for up to 4 days**.