Place the water in a large saucepan and add the salt.

Bring to a rapid boil and add the broccoli.

Steam for 6 minutes and drain well when finished.

Place the butter in a large skillet over medium heat.

Let the butter completely melt.

Add the onion and mushrooms.

Cook until the onion becomes tender about 5 minutes and drain well.

Place the broccoli, onion, mushrooms and water chestnuts together in a large mixing bowl.

In a small saucepan over low heat stir the Velveeta cheese and mushroom soup together.

Cook until the cheese is completely melted and mixture is smooth being sure to stir constantly so the cheese doesn't burn.

When smooth add the garlic salt and pepper.

Stir well.

Pour over the broccoli.

Allow the mixture to cool to room temperature.

Place mixture into freezer containers.

Freeze for up to 1 month.

When ready to bake place in the refrigerator to thaw overnight.

Preheat oven to 350°F

Lightly spray a 2 qt casserole with a non stick cooking spray.

Place the broccoli mixture in the casserole dish.

Bake 30 minutes.

Sprinkle the top with the cheddar cheese and continue baking 5 more minutes or until cheese has melted completely.