Heat oven to 350ºF. Spray 2-quart baking dish with no-stick cooking spray; set aside.
Combine bread cubes and 2 tablespoons of melted butter in a bowl; toss to coat.
Spread in an even layer on baking sheet.
Bake, turning cubes halfway through, for 20 minutes or until cubes are crisp and beginning to brown.
Melt 1 tablespoon of butter in 10-inch skillet over medium heat until sizzling.
Add Swiss chard and cook for 5 minutes or until wilted. Remove from heat.
Combine 3 cups milk, eggs, 1 teaspoon mustard, 1/2 teaspoon salt and 1/4 teaspoon pepper in a bowl; beat with whisk.
Stir in toasted bread cubes, cooked Swiss chard and chopped ham.
Spread egg mixture into prepared baking dish.
Bake for 50-55 minutes or until knife inserted in the center comes out clean.
Melt 1 tablespoon butter in small saucepan over medium heat until sizzling.
Add flour and 1/4 teaspoon pepper; cook 2 minutes.
Stir in 1 cup milk and 1 tablespoon mustard with whisk. Cook until bubbly around edges and slightly thickened.
Remove from heat and stir in cheese until melted.
Pour sauce over serving of egg bake. Enjoy!