Preheat oven to 350°F.

Heat a large skillet over medium heat.

Add two tablespoons of butter and the vegetable oil to the skillet, then add the broccoli and onion. Saute for ten minutes. Stir occasionally.

Transfer the cooked vegetables to a rectangle baking dish.

Return the skillet to the burner to make the cheese sauce.

Make a roux by adding ½ a stick of butter to the skillet then mix in the flour. Cook the flour mixture for about 3 minutes.

Next, add the milk to the flour mixture and combine.

Stir constantly and simmer until the mixture thickens to make a white sauce.

Season with salt, pepper and garlic powder.

Add the grated cheese and stir to combine. Simmer until the cheese has melted and the sauce is smooth.

Pour the cheese sauce over the vegetables in the baking dish.

Melt two tablespoons of butter in the microwave.

Crumble butter crackers in a small bowl then pour the melted butter over the crackers and stir to combine.

Top the casserole with the buttery cracker crumbs.

Bake 25-30 minutes.