Lemony Sweet Potato Pie

3 egg yolks
1 cup sugar
1 tbsp flour
1 1/2 cup milk
1/2 tsp lemon extract
1 tsp lemon peel,grated
2 tbsp butter,at room temperature
1 cup sweet potatoes,mashed,cooked
1 pie shell,unbaked,
1 sweetened whipped cream

Preheat oven to 400F.

Beat egg yolks with sugar and flour. Add milk, lemon extract, lemon peel, butter, and mashed potatoes; beat until well blended. Pour into unbaked pie shell and place on middle rack of preheated oven.

Bake 10 minutes, then reduce heat to 325F and continue to bake until pie is firm. Serve warm topped with well-chilled sweetened whipping cream. Servings: 8