Crumble salted crackers into a small bowl and mash them with butter until soft. Place steamed cauliflower into a 9x13 inch casserole dish.
In small saucepan, combine milk and mayonnaise with wire whisk. Bring the mixture to a boil; boil for 1 minute. Remove the pan from the heat and stir in cheese until melted. Pour this sauce over the cauliflower. Crumble the butter and cracker mixture over the cheese and cauliflower.
Place the casserole into the preheated oven and broil until golden brown.
