Add one teaspoon of olive oil to a frying pan over medium-high heat. Once hot, add the spinach and cook until wilted. Once cooked, drain the spinach under cold water until cool to the touch. Squeeze all the water out of the spinach and place on a cutting board. Roughly chop the spinach and set aside.
Beat the eggs in a large bowl with the milk, salt and pepper until no streaks of whites or yolks remain. Add two teaspoons of olive oil to a frying pan over medium heat. Add half the egg mixture and then sprinkle on half of the spinach. Fry until the bottom of the omelette is golden brown, flip, then fry for another minute, or until fully cooked.
Once cooked, set aside and cut into sixths. Repeat this process for the remaining egg mixture. Let the eggs cool completely before assembling the sandwiches.
Preheat the broiler to 500 degrees F. Arrange the English muffins cut-side up on a baking tray. Broil in the oven for 2-3 minutes, or until they are toasted and golden brown.
Next assemble the sandwiches. Add a teaspoon of mayonnaise to one side of the toasted English muffin. Top with a slice of the egg and spinach omelette, followed by a slice of ham, then a spice of cheese. Add the other half of the English muffin and press down gently. Repeat for the rest of the breakfast sandwiches.
Once all the sandwiches are assembled, wrap each sandwich individually in parchment paper. Once all the sandwiches are wrapped, place 6-8 sandwiches into a large freezer bag. Let freeze completely overnight.
When you want to cook a breakfast sandwich, simply remove it from the freezer, and place on a microwave-safe plate (still in it's parchment wrapper). Heat in the microwave for 1 minute and 30 seconds, or until warmed through.
Enjoy straight away with your morning tea or coffee!