Allow potatoes to thaw. Blend soup, cheese, yogurt and sour cream in large bowl. Saute chopped onions in 1/2 c melted butter for 7 minutes over medium heat. Combine onions with soup mixture and thawed potatoes. Stir to coat potatoes evenly. Spray 9x13 glass casserole dish with vegetable oil spray. Spoon potato mixture into glass casserole. Stir the other 1/2 cup melted butter and bread crumbs together in a separate bowl. Distribute these crumbs over the top of the potato mixture. Bake in preheated oven at 425 degrees for 30 minutes. Then cover dish with foil and continue cooking for 30 more minutes.
I agreed to bring a potato dish for a pot luck at work. I had a very busy week and came home tired the evening before I had to bring this food so I decided to make do with what I had in the home. I googled a recipe for a casserole but found I did not have the correct ingredients. But made do with what i had in kitchen.