hey i use to work at boston pizza and for all those that want to know here is the recipe.. it is no longer made fresh.. i heard they now get it pre-made .. but this is how we use to make it:

BOSTON PIZZA'S REAL CACTUS CUT POTATO DIP

12 oz Cesar dressing (the one we used was pretty thick)
24 oz Sour cream (again it was pretty thick)
3 oz chopped green onions
3 oz Parmesan cheese
2 tsp chilli flakes

This makes a large amount you might want to fool around to get your desired portion.