Hot Potato Salad

6-8 medium potatoes
3 Tbsp butter, melted
3/4 tsp dry mustard
1 1/2 cups milk
1 tsp salt
1/4 tsp pepper
3/4 cup mayo
1/2 lb Velveeta cheese, cubed
1/2 cup onion, chopped

Cook, cool, and cube potatoes. Mix butter, mustard, salt, pepper and milk. Boil one minute then remove from heat and add mayo and Velveeta cheese. Stir until melted. Add onion. Pour over potatoes in ovenproof casserole dish. Bake 350 degrees for 45-60 minutes.