Preheat the oven to 350°F. Line a 12-cup muffin tin with paper liners.
Combine the ricotta, cream cheese, sour cream, egg, sugar, cocoa and flour in a food processor. Purée until smooth. Divide the mixture among the prepared muffin cups.
Set the muffin tin in a larger pan. Pour enough hot water into the pan to come halfway up the sides of the muffin cups.
Bake in the center of the oven for 20 minutes. Remove and sprinkle the marshmallows and chocolate chips evenly over the cheesecakes. Return to the oven and bake for 5 minutes longer, or until the marshmallows and chocolate chips begin to melt.
Remove the muffin tin from the water bath and cool on a rack. Chill well before removing the paper liners and serving.
I like these really nice and cold. It makes the cheesecake texture so nice and creamy!