First, spray the inside of 4 4-ounce ramekins with cooking spray. Then, lay large pieces of plastic wrap (enough to hang over the edge and cover the ingredients once added). Now, spray the plastic wrap.
Next, bring a saucepan of water to a boil, add a handful of salt, and toss in the macaroni.
Cook the macaroni for 6 minutes, or 2 minutes shy of the total cooking time called for on the package. Add the broccoli at the 4 minute mark, or when the pasta has only 2 minutes left to cook.
Wipe out the pot you cooked the macaroni and broccoli in, and return it to the stove. Turn the heat to medium.
Add the butter, and once melted, whisk in the flour. Whisk until dissolved and cook for about 1 minute.
Next, stir in the mustard powder, garlic powder and milk. Bring this mixture to a simmer, and cook until it coats the back of a wooden spoon when stirring.
Turn off the heat, and stir in the cheese until it melts.
Finally, add the macaroni and broccoli back to the pot with the sauce, and stir very well to coat.
Divide the mixture between the ramekins, cover tightly with plastic wrap, and freeze overnight.
The next day, remove the frozen food from the ramekins, stack the food in a freezer-safe gallon-size plastic bag for up to 3 months.
To serve, defrost in the microwave (at 50% power) for 4 minutes, until heated through, or defrost overnight in the fridge before microwaving until warm.