1 lb. cream cheese, softened
1 lb. Ricotta cheese
1 1/2 c. sugar
4 lg. eggs, room temperature
1/4 c. unsalted butter, melted and cooled
3 tbsp. flour
3 tbsp. cornstarch
2 1/2 tsp. vanilla
2 c. sour cream

In a large bowl with a mixer, cream the cream cheese, Ricotta cheese and sugar. Beat in eggs, one at a time, beating well after each egg is added. Add butter, flour, cornstarch and vanilla, beat until well combined. Fold in sour cream. Turn into ungreased 9 inch spring form pan. Bake in center of a preheated 325 degree oven for 1 hour. Turn off heat (DO NOT OPEN OVEN DOOR) and let the cake remain in oven for 2 hours. Set on rack in pan and cool completely. Chill for at least 2 hours, loosely wrapped. Remove from pan and transfer to a plate to serve.