Grandma Connie's Patrician Potatoes

8 - 10 potatoes, cooked and mashed
1 (8oz.) cream cheese
1 (8oz.) sour cream
1 tsp. garlic salt
1 small onion, grated finely (optional)
Salt and Pepper to taste
*If necessary can be put in pan and warmed in 350 oven for 20-30 minutes.