Londonderry Cheesecake

1. Early in the day: 1. In a medium bowl, combine flour, 6 tablespoons sugar, and 1 teaspoon grated lemon peel.
2. With pastry blender or two knives used scissor fashion, cut in butter or margarine until mixture resembles coarse crumbs.
3. With a fork, stir in 2 egg yolks and 1/2 teaspoon vanilla to form a very stiff dough.
4. Chill 30 minutes.
5. Preheat oven to 425 degrees, F. 2. Press one third of the chilled dough evenly into the bottom of a 9 inch springform pan. Bakei 8 - 10 minutes until golden brown.
6. Cool. Press rest of dough around sides of pan to within 1 inch of top. Do not bake.
7. 3. In a large bowl, with mixer at high speed, beat cream cheese until smooth' gradually add Cheddari cheese, beating until well blended - about 5 minutes.
8. Occasionally scrape bowl with rubber spatula.
9. 4. At medium speed, gradually beat in 1/2 teaspoon grated lemon peel, 1/2 teaspoon vanilla, 1 3/4 cups sugar, 2 egg yolks, and remaining ingredients until blended.
10. Beat 5 minutes, occasionally scraping bowl.
11. 5. Pour mixture into crust.
12. Bake 10 minutes.
13. Turn oven control to 300F and bake 1 hour and 15 minutes longer or until top is firm when lightly pressed with a finger.
14. 6. Cool in pan on wire rack.
15. Cake will sink in center, leaving cracks around crust.
16. With spatula, loosen pan side and remove.
17. Loosen cake from pan bottom; slide onto plate; chill.
18. Makes about 12 servings.