Mix 1 cup sugar with 2 tablespoons flour and enough milk to moisten well. Spread mixture on bottom of unbaked pie shell. Pour about 2 cups milk over the sugar mixture. Add 1/2 teaspoon vanilla and use spoon to see that all sugar mixture is dissolved. Dot with butter and bake in moderate oven (350 degrees) for 35 minutes or until the pie sets (it should still jiggle but not be liquid).