Preheat oven to 400 F, lightly grease a 9x13 casserole dish and set aside.

Blanch frozen broccoli in boiling salted water for 1 minute, then drain and set aside until needed.

In a medium saucepan over medium heat, add the velveeta, mayo, sour cream, butter, garlic powder, dehydrated onion, salt and pepper and stir frequently until smooth and melted; set aside.

In a small bowl, stir together the crushed ritz and the melted butter; set aside.

Add the broccoli to the prepared casserole dish.

Pour the cheese sauce on tip and mix to coat all broccoli.

Sprinkle cheese evenly over the broccoli mixture, then sprinkle the ritz mixture on top.

Bake in preheated oven 20 minutes, or until the casserole is bubbling and the ritz crackers are golden brown.

Allow to cool 5 minutes before serving.