Layer ham, turkey, and cheese between two slices of bread.
In a bowl, whisk together the egg and milk.
Heat a skillet over medium heat and add butter.
Dip the sandwich into the egg mixture, coating both sides.
Place the sandwich in the skillet and cook until golden brown, about 3-4 minutes per side.
Remove from skillet and place on a paper towel.
Dust with powdered sugar.
Slice the sandwich in half.
Serve with a side of jam.
Enjoy your delicious monte cristo sandwich!