The Sauce Base:
In a large saucepan melt butter on medium low heat.
Sauté garlic in butter until it just starts to turn golden, about 2-3 minutes.
Quickly add flour, dried mustard, and black pepper, whisking continually.
Continue whisking until a deep golden roux is formed, about 2-3 minutes.
Slowly whisk in the milk.
Return to medium-low heat, bring to a near boil, remove from heat, and then stir in cheese quickly.
Continue whisking until your cheese sauce is smooth and creamy.
Allow to cool.
While this is cooling, bring 6 cups of water to a boil in a medium pot. Once boiling, remove from heat and toss your dry potatoes into the pot with the water, making sure they are all completely covered with the water. Let this sit for 10 minutes then pour water and soaked potatoes into a strainer. Rinse potatoes with cool water until potatoes are nice and cold. Set aside.
To make right now:
Preheat oven to 350 degrees. Add 1 ½ cups of water to cheese sauce. Then add soaked potatoes and broccoli and mix it all up well. Add to a 9x13 baking dish and cook for 50-60 minutes or until golden and bubbly on top. Add topping on and then bake for an additional 10 minutes. Then enjoy!
To make and freezer for later:
Make sure the cheese sauce is cool. Sometimes if I’m in a big hurry I will quick cool the cheese sauce by putting the pot on top of a bowl of ice and whisking the sauce until its cool (about 5 minutes). Then combine cheese sauce, cooled soaked potatoes and frozen broccoli into a bowl, and mix well. Then add to freezer safe bag, seal, label and freeze. Make the topping, seal and freeze with the main meal.
The day before cooking it allow it to thaw for 24 hours in your fridge. On the cooking day preheat oven to 350 degrees. Then add in 1 ½ cups water to your freezer bag, seal and swish it until it’s all incorporated well. Then pour into 9x13 baking dish and make sure none of the potatoes are sticking out of the sauce. Bake for 50-60 minutes or until golden and bubbly on top. Add the topping on and then bake for an additional 10 minutes.