Preparation

• Melt the butter in a 10-inch Dutch oven or other heavy, deep pot over medium heat. Add the crushed crackers, black pepper, and kosher salt and stir to coat with the melted butter. Continue to toast over medium heat, stirring often, until golden brown, 2 to 4 minutes.
• Transfer the toasted cracker crumbs to a plate to cool and wipe the pot clean of any tiny crumbs.
• In the same pot, melt the butter over medium heat. Once melted, add the ground mustard, pepper, and cayenne (if using). Stir to combine with the butter and lightly toast until fragrant, 15 to 30 seconds.
• Add the water, half and half, and kosher salt to the butter mixture and stir to combine. Bring the mixture to a boil over high heat, uncovered.
• Once boiling, stir in the elbow macaroni, adjusting the heat as needed to maintain a rolling boil (but not boil over). Continue to cook uncovered, stirring every minute or so, until the pasta is tender and the liquid is reduced enough to reveal the top layer of elbows, 6 to 9 minutes.
• Add the cream cheese to the pasta mixture and stir until almost completely melted. Add the shredded cheddar and Monterey Jack and stir until the cheeses are completely melted and saucy.
• Taste the mac and cheese. Season with more salt and pepper as needed. Serve immediately topped with the toasted Ritz topping, if using.