Preheat oven to 375°F . Line a rimmed baking sheet (or 9 x 13 baking pan) with foil, leaving some overhang to use as handles. Spray liberally with non-stick cooking spray.
Whisk together the eggs, milk, mustard, chives, parsley, salt and pepper in a medium mixing bowl.
Pour the egg mixture onto the baking sheet or pan and carefully transfer to the oven. Bake for 10 - 12 minutes or until the egg mixture is set.
Cool slightly and use the foil handles to remove the baked eggs to a hard surface. Use a pizza cutter or sharp knife to cut the eggs into 6 rectangles and lay pieces between English muffins with ham and cheese. Allow sandwiches to cool completely.
Slide each sandwich into a labeled wax paper sandwich bag, Fold over bag opening to seal. Place wrapped sandwiches into a large plastic freezer bag or container. Freeze up to 3 months. Top with a lettuce leaf before serving.