Preheat the oven to 400 degrees F. Line eight standard size muffin or 12-13 miniature (2 inch size) cups with paper liners.
Toss the chocolate chips with 1 teaspoon of the flour and set aside. Put the remaining flour, baking powder, baking soda and salt in a bowl and whisk for 15 seconds.
In a mixing bowl, beat the butter, oil and sugar with an electric mixer. Add egg and stir until blended, then beat with the mixer until light and fluffy, scraping the bowl. Beat in the orange zest, rum and ricotta cheese.
With a heavy duty scraper, stir in the flour mixture. If batter seems dry (more like cookie dough than muffin dough) add milk 1 tablespoon at a time until the batter is about the consistency of ricotta or drop biscuit batter.
Pile the muffin batter into muffin cups. It should be pretty thick..
Put the muffins in the hot (400 degree) oven, then immediately reduce temperature to 375 degrees F. Bake for 20 minutes or until a meat thermometer inserted in a muffin registers 205 F. If making the smaller size 2 inch muffins, preheat to 375 and bake at 375 for 20 minutes.