Foryoueats: Ham Casserole

Ingredients

• 3 tablespoons unsalted butter
• ½ cup shredded Monterey Jack cheese
• 1 ½ pounds potatoes, sliced about 1/4-inch thick
• 2 cups cooked ham steak, cubed
• 2 cups whole milk, slightly warmed
• 1 ½ teaspoons mustard powder
• 1 teaspoon cayenne pepper
• 1 teaspoon pepper
• 1 teaspoon salt
• 3 cloves garlic, minced
• 3 tablespoons all-purpose flour
• 1 medium onion, diced
• chives for garnish optional