Whisk eggs, egg whites, ¼ c. cheddar cheese, salt and pepper. Set aside.

Cook bacon in a 10-inch nonstick oven-safe skillet slowly over medium heat until crisp. Remove to a paper-towel-lined plate to cool a bit, then crumble (let sit).

Pour off all but 2 tablespoons bacon fat from skillet, reserving the excess.

Add hash browns (before adding, squeeze tightly with a clean towel to remove as much moisture as possible). Cook 3 minutes, stirring until browned. Pour 1 tablespoon reserved bacon fat (or use oil if none remains) around perimeter of skillet, then stir in spinach, bacon and eggs. Cook 2 minutes and sprinkle with ¼ cup shredded cheddar cheese.

Transfer skillet to preheated 400 degree oven for 10 minutes or until eggs are cooked.

Remove skillet from oven; using a knife or spatula to release frittata from sides and carefully slide onto a plate. Slice into 6 wedges.