Prepare pierogies according to box directions. In a deep skillet or larget saucepan, melt butter over medium heat. Whisk in flour over low heat until well blended. Add milk, paprika, salt, and pepper.
Cover until mixture thickens and starts to boil. Remove from heat and stir in cheddar cheese until melted.
Pour cheese mixture over pierogies in stock pot and toss gently to coat. Pour into a 2 quart baking dish* and sprinkle breadcrumbs over top. Bake at 375 for about 15 minutes.
*Note: the original recipe says to place in individual ramekins which I don't have. In the future I plan on trying this recipe with ramekins, it's a good way to portion control my boys lol.