1In 10-inch skillet, heat oil over medium-high heat. When oil is hot, add onion and mushrooms; cook and stir until onion is softened and slightly caramelized.
2Add frozen potatoes; stir to combine. Cook about 10 minutes or until potatoes are golden brown.
3Add egg whites; cook and stir about 2 minutes or until eggs are fully cooked. Add cheese, salt and pepper.