In a pan, heat oil and sauté the onion, spinach, and mushrooms for 1-2 minutes and take off heat.
In a measuring cup, pour in the egg whites and the salt and pepper. Whisk to combine. Pour the cooked ingredients into the egg whites and mix.
Line a muffin pan with silicone molds or use a non-stick coconut oil cooking spray. Mold the ham into the bottoms of the tins and then pour the egg white mixture into each cup of ham. Add the chopped cheddar cheese on top.
Bake for 30-35 minutes, or until cooked entirely through. Garnish with parsley, if desired, and serve!
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