Preheat the oven to 400F.

Melt half of the light butter in a large, deep frying pan over medium heat. Add the flour, and whisk. The flour and butter will mix and form clumps. Cook for 1-2 minutes.

In the meantime, bring a large pot of water to a boil.

Add milk to the roux (butter & flour), whisking as you pour it in. Continue to cook over medium heat, whisking often to break down the clumps. Cook for 10 minutes (might need to scale time) or until the sauce thickens significantly. Add the seasonings, stir to combine.

Chop the colby jack cheese into small pieces. Shred the cheddar. Add both cheeses to the mixture, whisking to help break them down and melt. Stir until all of the cheese has melted, add gouda, then set aside until the pasta is done.

Return to the pot of boiling water. Add the pasta; cook for 2 minutes less than the package directions advise.

Chop the broccoli into bite-sized florets. During the last two minutes of cooking, add the broccoli florets to the water. (If using frozen broccoli, it does not need to boil. Just defrost the florets and add them to the dish.)

Using a slotted spoon, remove the cooked pasta and broccoli from the pot and add them to the cheese sauce. Stir thoroughly so that all ingredients are well mixed.

Spray a casserole dish with nonstick cooking spray, and then pour the mac and cheese in. Smooth out the top.

Add the remaining butter to a small bowl and melt it. Stir in the breadcrumbs. The mixture will resemble wet sand. Sprinkle the breadcrumbs over the casserole dish and then pop it in the oven.

Cook for 20 minutes or until the top is lightly golden brown.