1. If you make your own crust, you will need 1 1/2 cups graham cracker crumbs, 6 tablespoons softened butter and 1/3 cup white sugar (for 1 crust). Just mix everything in a bowl and press the mixture into a 9-inch pie plate.
2. Preheat oven to 325 degrees F (165 degrees C).
3. In a large bowl, using an electric mixer, beat ricotta, butter, powdered sugar and cream cheese until smooth. Beat in heavy cream.
4. With mixer on low speed or a whisk, add vanilla and eggs one at a time.
5. Pour batter over crust.
6. Bake for 55 to 60 minutes, or until filling is set (a toothpick inserted into the center of the cake should come out clean).
7. Melt the chocolate: chop it and place in an oven safe bowl; fill a saucepan with hot water (so that water doesn't touch the bowl with chocolate if you place it over the water); heat the saucepan until it begins to simmer, then place the bowl with chocolate on top of the saucepan; when the chocolate begins to melt, stir it with a spatula until smooth.
8. Spread the melted chocolate over the baked cake.
9. Chill several hours or overnight.