Preheat oven to 350 F. Grease muffin tins or line with cupcake liners.
Mix together butter and sugar until creamy. Beat in egg and vanilla.
Mix in mashed banana and sour cream until well blended.
Add flour, baking soda, salt and cinnamon until well combined.
Stir in ½ cup chocolate chips.
Use a cookie scoop to spoon batter into prepared muffin cups, greased or paper liners. Fill almost to the top. This will make for nice rounded tops. Sprinkle with remaining chocolate chips.
Pour the batter into your prepared loaf pan. Bake for 50-70 minutes at 350°F or until a tester inserted into the center comes out clean.