Step 1

Preheat the oven to 375˚. Butter a 9-by-13-inch baking dish. Bring a large pot of salted water to boil. Add the cauliflower and cook 2 minutes. Add the broccoli and cook until both vegetables are crisp-tender, 2 to 3 more minutes. Drain and let cool.

Step 2

Melt 2 tablespoons of the butter. Combine the melted butter, crushed crackers and paprika in a small bowl. Set aside.

Step 3

Cook the bacon in a large dutch oven over medium heat, turning, until crisp, about 8 minutes. Remove to paper towels to drain. Chop and set aside.

Step 4

Pour out the bacon fat from the pot and reserve it, then wipe the pot clean. Return 1 tablespoon bacon fat to the pot along with the remaining 2 tablespoons butter. Once the butter is melted, add the garlic and cook 30 seconds. Whisk in 1 teaspoon salt, the ground mustard, lemon zest and cayenne. Whisk in the milk until smooth. Bring to a simmer, whisking, and cook until thickened, about 3 minutes. Remove from the heat and whisk in the cream cheese until smooth. Whisk in the cheddar until smooth. Stir in the broccoli, cauliflower and bacon.

Step 5

Transfer the mixture to the baking dish and sprinkle with the cracker crumb mixture. Cover with foil and bake until bubbly, about 20 minutes. Uncover and bake until golden, 20 to 25 minutes. Let sit 15 minutes before serving.