1In a small bowl, mix the mayonnaise and Dijon mustard together.
Spread the mayonnaise and mustard mixture evenly on one side of each slice of bread.
On four slices of bread, layer a slice of Swiss cheese, a slice of ham, a slice of chicken breast, and another slice of Swiss cheese.
Top each with the remaining slices of bread, spread side down, to form a sandwich.
In a shallow dish, whisk together the eggs and milk until well combined.
Place the flour in another shallow dish.
Carefully dip each sandwich in the flour, coating both sides, then dip into the egg mixture, ensuring both sides are covered.
In a large skillet, melt the butter over medium heat.
Cook each sandwich in the skillet for 3-4 minutes on each side, or until the bread is golden brown and the cheese is melted.
Remove from the skillet and let cool slightly before serving. Enjoy your Monte Cristo Chicken Sandwich!