Banana Espresso Muffins

1 1/2 cups ripe mashed bananas 
1/2 cup sugar 
1/4 cup packed brown sugar 
1/2 cup melted, unsalted butter 
1/4 cup milk 
1 egg 
1 1/2 cups flour 
2 tsp instant espresso 
1 1/2 tsp baking soda 
1 tsp salt 
1 cup chocolate chips 

1. Preheat oven to 350F. Grease a muffin tin. 
2. In small bowl, beat together bananas. sugars, butter, milk and egg. 
3. In a separate bowl, whisk together flour, espresso, baking soda and salt. Fold in wet ingredients. Fold in chocolate chips, just until combined. (I never use a mixer of any sort for this recipe, just my wooden spoon!) 
4. Pour batter into muffin tin and bake for 20-25 minutes, or until an inserted toothpick comes out clean.