Heat oven to 375°F. In 10-inch ovenproof nonstick skillet, cook beef over medium-high heat, stirring frequently, until brown; drain. Stir in hot water, butter, potatoes (from Hamburger Helper box) and bell pepper. Heat to boiling over high heat, stirring constantly, until butter is melted.
Reduce heat to medium; press potato mixture evenly with back of spatula. Cook uncovered 6 minutes, without stirring, until liquid is absorbed.
In medium bowl, beat eggs and 1/2 teaspoon salt with whisk until well combined. Pour eggs over potatoes in skillet, stirring to evenly combine. Cook 4 to 5 minutes, gently lifting edges of cooked portions with spatula so that uncooked egg mixture can flow to bottom of skillet, until bottom is set and most of egg is cooked. Place skillet in oven.
Bake 8 to 10 minutes or until eggs are fully cooked.
In medium bowl, mix milk and topping mix (from Hamburger Helper box). Cut frittata into wedges. Drizzle with topping mixture. Season to taste with salt and ground black pepper.