Prep the broccoli (this can be done several days ahead)Sprinkle the broccoli florets with a pinch of salt.

Working in batches, add the broccoli florets to a microwave-safe bowl. Cover and microwave the broccoli for 4-5 minutes until bright green and still gives a little resistance when pierced with a fork. Try not to overcook your veggies at this stage, the broccoli will finish cooking during baking.

Pour out any excess water that may be in the bowl after steaming. Transfer the steamed broccoli to an 8" x 8" baking dish.

Make The Cheese sauce:In a 2 quart or larger saucepan, melt the butter over medium heat and add the flour.

Whisk the butter and flour until combined and cook until the mixture smells nutty (about 1 minute).

Slowly add the milk. Add a little bit at a time, and whisk continuously making sure the sauce is smooth after each addition of milk. 

At first, when the milk hits the roux, it will ball up like dough, that's what you want. As you add more milk, the mixture will turn into a paste, and then with the last addition of milk, turn into a smooth and silky sauce.

Turn the burner up to medium-high heat and add the garlic powder and a few cracks of pepper.

Bring the sauce to a simmer. Gently simmer for 45-60 seconds until slightly thickened, whisking continuously to prevent scorching.

Remove the white sauce from heat. Working in two batches, add in 8 oz of the cheddar cheese. 

Whisk the cheese in slowly until just melted between each addition.  

Once 8 oz of cheese has been added, give a final whisk to make sure the sauce is completely smooth. The sauce will have thickened quite a bit, but will still be pourable (you can add a little more milk if the cheese sauce is too thick to pour).

Give the cheese sauce a taste and season with more salt, pepper, and garlic powder if needed.

Assembling and baking the casserole:Preheat the oven to 400º.

Pour the cheese sauce evenly over the broccoli. 

Coarsely crush the Ritz crackers and sprinkle over the top of the broccoli and cheese mixture. Top with the remaining 4 oz of shredded cheddar cheese.

Bake the casserole in a 400º oven for 15-20 minutes until the cheese on top has melted, browned and the edges are bubbling.

Remove the casserole from the oven and allow it to sit for 15 minutes before serving.