Quick and Easy Corned Beef Omelet

Name: Quick and Easy Corned Beef Omelet
Ingredients: 1 teaspoon olive oil; 1 tablespoon minced onion; 1/4 cup finely diced potatoes (from 1 small red or yellow potato); 1/4 cup finely diced corned beef; Few pinches salt; 1 teaspoon unsalted butter; 2 large eggs; 2 tablespoons milk; 2 tablespoons grated Parmesan cheese; Pinch salt and pepper; Fresh parsley, garnish