In large pot, combine potatoes with enough salted water to cover. Over high heat, bring to boil; cook until potatoes are tender, 15-20 minutes. Drain and return to pot.

Meanwhile, in large nonstick skillet, melt 1 T. butter over medium heat. Add chopped pepper; cook, stirring occasionally, until almost tender, about 8 minutes. Add scallions; cook, stirring occasionally, 2-3 minutes. Remove skillet from heat; reserve mixture.

In microwave-safe measuring cup, combine half-and-half and remaining 3 T. butter; on high, microwave mixture in 15-second intervals until hot and butter is melted, about 1 minute. Stir hot half-and-half mixture, salt and pepper into potatoes; mash.

Stir in chopped parsley and pepper and scallion mixture. If desired, serve topped with additional butter.