Cauliflower-Broccoli Salad

1 lg head cauliflower
1 lg bunch broccoli
1 sm onion
1 pkg frozen peas
2 cups mayo
1 cup sour cream
1 tsp garlic powder

Mix mayo, sour cream and garlic powder in small bowl. Break up broccoli and cauliflower into small bite sized florets. If using pea pods, cut into small pieces. Toss sauce with cauliflower, broccoli and onion. Mix well. Add peas last and refrigerate at least four hours or overnight.