2 tbsp. flour
2 egg yolks, lightly beaten
1 c. sugar
1 baked pie shell
1 1/2 c. boiling water
2 tbsp. butter
3 tbsp. vinegar

Combine flour and sugar. Stir in remaining ingredients adding the boiling water last. Cook in double boiler until thickened. Pour into baked pie shell. Top with meringue if you wish.