Whisk together the eggs, milk, vanilla extract, maple syrup and salt in a shallow dish and set aside. Then mix the dijon mustard into the mayonnaise.
Spread a small amount of the mayonnaise mixture onto each slice of bread. Add a ⅓ cup of cheese onto the bottom slices, setting aside a small amount from each one to attach the top slice of bread. Add two slices of ham on top of the cheese, then add the rest of the cheese you removed before. Place the top slices on top.
Add 1 tablespoon of olive oil to a frypan or skillet and heat over medium-low heat. Add about 30 grams of butter and allow it to melt slowly.
Dip each side of the sandwich into the egg mix, allow the excess to drip off and place into the frypan. (You should be able to get two sandwiches cooked at once depending on the size of your pan). Cook on medium-low heat for about 2 minutes a side or until each side is a dark brown colour and crispy.
Place the cooked sandwiches onto some paper towel and pat down gently to remove excess oil and butter. Then cut in half and serve with extra maple syrup for dipping.