Sweet Potato Pie

4 eggs, separated

2 cups sugar

3 cups cooked, mashed sweet potatoes

1/2 cup softened margarine or butter

2 cups milk

2 teaspoons vanilla extract

1 teaspoon ground nutmeg

1 1/2 teaspoons ground cinnamon

2 (9 inch) unbaked pie shells

Beat egg yolks until thick. Gradually add sugar; mix well. Add next 6 ingredients and mix well. Beat room temperature egg whites until stiff peaks form; fold into sweet potato mixture. Pour into pie shells and bake at 350° for 45 minutes or until set.