Steam broccoli florets just until fork tender. Drain well, set aside.
In a large deep pot, heat milk, water and salt until steaming, just before it boils. Watch carefully so it doesn't boil over. Add the dry macaroni, stir to prevent sticking to bottom.
Cook uncovered over medium-high bubbling for 12-15 minutes or just until al dente and tender, stirring occasionally. Do not drain. Turn heat to low.
To the pot add butter, cream cheese, black pepper, granulated garlic or garlic powder, onion powder and ground mustard. Stir until fully combined and melted.
Add shredded cheddar cheese, mix again until the cheese has completely melted, then fold in the steamed broccoli.
Remove from heat and serve immediately.
Notes
Pasta: You can use any similar size pasta. Classic elbow macaroni, medium shells or penne rigate. Keep in mind if you switch to a large pasta that the sauce may need to be adjusted.
Cheese: You can make broccoli mac and cheese with other varieties of cheese. Try mild cheddar cheese, colby jack cheese, mozzarella cheese or pepper jack cheese for spice.
Seasoning: You can add color to the macaroni and cheese adding a dash or turmeric, 1-2 teaspoons Dijon mustard or yellow mustard.
Protein: You could turn this into a one-pot meal and stovetop casserole by adding cubed chicken, ham or crispy bacon.
Herbs: You expand the flavor profile adding rosemary, chives, or parsley.
Use Fresh or Frozen Broccoli: You can steam your own broccoli florets on the stovetop or use a steamable bag of broccoli. I highly recommend using florets and not broccoli cuts.
Baking Broccoli Mac and Cheese: You could make this dish in advance and pour it into a 13x9-inch baking dish. Top it with additional shredded cheddar cheese and 1-2 tablespoons of Parmesan cheese and buttered panko breadcrumbs, then bake it in a preheated 350°F oven for 30 minutes or just until bubbly and lightly golden brown.