Preheat the oven to 400F. Spray the inside of a 1.5-quart casserole dish with olive oil spray.
Cook the cauliflower florets in boiling water for 3 minutes, and then drain well.
Whisk together the cream cheese, milk, Frank’s RedHot sauce, onion powder, garlic powder, salt, Worcestershire sauce, Dijon mustard, and black pepper in a medium saucepan over medium heat. Once the sauce is smooth, whisk in the shredded cheese a handful at a time until the sauce is smooth.
Add the Ritz crackers to a zip-top plastic bag and crush. Add the thyme, black pepper, and butter, seal the bag, and shake it around to mix.
Stir together the cauliflower and cheese sauce. Pour it into the prepared casserole dish. Sprinkle the cracker topping evenly on top.
Bake until the casserole is bubbling outside and the topping is golden, about 15 minutes.