Preheat oven to 350 degrees F (175 degrees C). Butter a 2 quart baking dish.
Rub pork chops with salt, pepper, and garlic powder. Melt butter in a skillet over medium-high heat, add chops, and brown on both sides. Remove from skillet. Place onions in skillet, and cook until browned. Pour in mushroom soup and milk; stir until blended. Remove from heat, and set aside.
Arrange sliced potatoes evenly in prepared baking dish. Arrange chops on top of potatoes. Pour soup mixture over chops.
Bake, covered, for 30 minutes in the preheated oven. Uncover, and bake 30 minutes more, or until potatoes are tender.