Preheat oven to 350°F. Line muffin pans with paper baking cups.
Stir oil and sugar with wooden spoon or spatula. Set aside.
Add bananas, eggs, milk, vinegar, baking soda, and salt to a blender jar and blend until smooth.
Pour half the banana mixture into the oil mixture with 1 cup of flour. Stir until just incorporated, then add the remaining banana mixture and flour. Stir until just incorporated. Stir in nuts, if using.
Make the cream cheese filling: stir (or use a hand mixer) together cream cheese and sugar until smooth.
Fill muffin cups with about 2 tablespoons of muffin batter. Add about 1/2 teaspoon of cream cheese to the center of each muffin, then top with another 1 tablespoon of batter. Sprinkle with chopped nuts on top, if desired.
Bake for 14-18 minutes until a toothpick comes out clean from the side of a muffin. Cool 5 minutes in pan then remove to a rack to cool completely.
Store in an airtight container for up to 3 days or freeze for up to one month.