1 For the crust, combine crushed graham crackers, walnuts, and cinnamon. Stir in melted butter. If desired, set aside 1/4 cup of the crumb mixture for topping. Press the remaining crumb mixture onto the bottom and about 2 inches up side of an 8- or 9-inch springform pan. Set aside.
2 For filling, in a large mixing bowl beat cream cheese, sugar, flour, and vanilla with an electric mixer until combined. Add eggs and egg yolk all at once, beating on low speed just until combined. Stir in milk and, if desired, lemon peel.
3 Pour filling into crust-lined pan. If desired, sprinkle with reserved crumbs. Place on a shallow baking pan in oven. Bake in a 375° oven for 45 to 50 minutes for the 8-inch pan, 35 to 40 minutes for the 9-inch pan, or until the center appears nearly set when shaken.
4 Cool in pan on a wire rack for 15 minutes. Loosen the crust from side of pan and cool 30 minutes more. Remove the side of the pan. Cool completely on wire rack. Cover and refrigerate at least 4 hours before serving.