Preheat oven to 350 degrees F. For sauce, melt the 3 tablespoons butter over medium heat in a medium saucepan. Cook onion and garlic in hot butter for 4 minutes or until tender.
Stir in flour, salt and pepper. Cook and stir for 1 minute. Stir in milk. Cook and stir for 7 minutes or until thick and bubbly. Remove pan from the heat. Stir in cheese until melted. Stir in canned peas and ham.
Arrange half of the canned potato slices in a greased 2-quart baking dish. Pour half the sauce over the potatoes. Repeat layers. Combine panko and the 1 tablespoon melted butter in a small bowl. Sprinkle over mixture in dish.
Bake, uncovered, for 30 minutes or until bubbly and topping is golden brown. Let stand for 10 minutes before serving.
All done! Now take a photo, rate it, and share your accomplishments!