Preheat the oven to 350. Lightly mist 12 cups in a muffin tin with cooking spray. Press a slice of ham into each cup of the muffin tin, arranging the edges to form a ham cup. Chop up the remaining ham (my slices were about ½ ounce each so I had around 3 ounces remaining) and set aside.

In a mixing bowl, combine the eggs, egg whites, milk, salt and pepper and whisk together until yolks and whites are fully combined and beaten. Add the reserved chopped ham, the spinach and half of the shredded cheddar and stir together to combine.

Spoon the egg mixture evenly into the ham cups and then top each cup with the remaining shredded cheese. Place the tin in the oven and bake for 18-20 minutes until the eggs are set.