Place cauliflower in a steamer basket set over simmering water. Cover and steam until just tender, about 5 minutes. Drain.
In a large Dutch oven, melt unsalted butter over medium-high heat. Add garlic and minced thyme; cook for 30 seconds. Add flour; cook until lightly browned, about 2 minutes. Gradually add milk, whisking until combined. Add salt, dry mustard, hot sauce, and pepper; cook, stirring constantly, until thickened, about 5 minutes. Remove from heat; stir in cheeses until melted. Stir in cauliflower. Divide mixture among 6 (8-ounce) ovenproof baking dishes.
In a small bowl, combine bread crumbs and melted butter. Sprinkle over cauliflower mixture. Place ramekins on a rimmed baking sheet.
Bake until bubbly, about 20 minutes. Garnish with thyme, if desired.
Recipe by Paula Deen Magazine at https://pauladeenmagazine.com/cauliflower-mac-cheese/