| 1. | Preheat oven to 325 degrees F (165 degrees C.) Wrap the outside bottom of a 10 inch springform pan with foil to prevent water seeping in while baking. |
| 2. | Cream together ricotta cheese, cream cheese and sugar until smooth. Mix in the eggs one at a time. Add flour one tablespoon at a time, mixing well. Stir in the sour cream and vanilla. Pour mixture into a 10 inch springform pan. |
| 3. | Place cheesecake in a large rectangular pan filled with 2 inches of hot water. Carefully put into preheated oven without spilling water. Bake for 90 minutes. |
| 4. | After 90 minutes turn oven off, but leave the cake in the oven for another 60 minutes (do not open door). |
| 5. | Cool on counter for 60 minutes and then refrigerate. Serve when thoroughly chilled. |
