Step 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.

Step 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.

Step 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.

Step 4

After 90 minutes turn oven off, but leave the cake in the oven for another 60 minutes (do not open door).

Step 5

Cool on counter for 60 minutes and then refrigerate. Serve when thoroughly chilled.