Easy Mashed Potato Casserole

2 teaspoons butter or margarine
16 medium green onions, sliced (1 cup)
1 med. Yellow or orange bell pepper, chopped (1 cup)
3 cups hot water
1 cup half-and-half or whole milk
¼ cup butter or margarine
1 package roasted garlic mashed potatoes (2 pouches)
1 ½ cups shredded cheddar cheese (6 oz)

Heat oven to 350 degrees. Spray 2 quart casserole with cooking spray. In 10 inch non-stick skillet, melt 2 teaspoons butter over medium – high heat. Cook onions and bell pepper in butter 1 minute, stirring occasionally. Remove from heat; set aside. In 2 quart saucepan, heat water, half-and-half, and ¼ cup butter to boiling; remove from heat. Stir in both pouches of potatoes (and seasoning) just until moistened. Let stand about 1 minute or until liquid is absorbed. Beat with fork until smooth. Spoon 1 1/3 cups of potatoes into casserole; top with half of the onion mixture and ¾ cup of the cheese. Spoon another 1 1/3 cups potato over cheese; carefully spread to cover. Sprinkle evenly with remaining onion mixture. Top with remaining potatoes; carefully spread to cover. Sprinkle with remaining ¾ cup of cheese. Bake uncovered about 30 minutes or until hot.