Step 1: Preheat the Oven - Preheat your oven to 350°F (175°C).
Step 2: Prepare the Muffin Tin - Line a muffin tin with parchment paper or muffin liners.
Step 3: Mix the Dry Ingredients - In a large mixing bowl, whisk together the flour, baking soda, salt, cinnamon, and nutmeg.
Step 4: Combine the Wet Ingredients - In another bowl, beat the egg and add brown sugar, vanilla, and olive oil. Mix in mashed bananas and milk.
Step 5: Combine Wet and Dry Ingredients - Pour the wet mixture into the dry ingredients and gently fold until just combined.
Step 6: Add the Chocolate - Fold in the chopped dark chocolate.
Step 7: Fill the Muffin Tin - Spoon the batter into the muffin tin, filling each cup about 3/4 full.
Step 8: Bake - Bake for 18-22 minutes, until a toothpick comes out clean.
Step 9: Cool - Let the muffins cool in the tin for 5 minutes before transferring them to a cooling rack.
