Harvard Beets

Mix 1/2 cup sugar, 1 Tbsp. cornstarch, and 1/2 tsp. salt. Add 1/2 cup vinegar, 1/3 cup boiling water, and cook until sauce is clear. Add 2 cups freshly cooked, drained, diced beets. Keep beets in sauce in warm place for 30 minutes. Add 2 Tbsp. butter and serve.