Preheat oven to 350°. In a small bowl, mix cornstarch and water until smooth. In a large saucepan, heat butter over medium heat. Stir in corn, evaporated milk, 3/4 teaspoon sugar and 1/2 teaspoon salt; bring just to a boil. Stir in cornstarch mixture; return to a boil, stirring constantly. Cook and stir 1-2 minutes or until thickened; cool slightly., In a large bowl, whisk eggs, milk, pepper and the remaining sugar and salt until blended. Stir in bread, onion and corn mixture. Transfer to a greased 8-in. square or 1-1/2-qt. baking dish., Bake, uncovered, 40 minutes. In a small bowl, toss Rice Krispies with melted butter; sprinkle over casserole. Bake 10-15 minutes longer or until golden brown. Freeze option: Cool unbaked casserole, reserving Rice Krispies topping for baking; cover and freeze. To use, partially thaw in refrigerator overnight. Remove from refrigerator 30 minutes before baking. Preheat oven to 350°. Bake casserole as directed, increasing time as necessary to heat through and for a thermometer inserted in center to read 165°.