Dice the cauliflower into bite-sized florets. Add the florets to a medium saucepan and cover with boiling water. Simmer for 4-5 minutes until just tender. Drain completely and set aside to steam dry.
Preheat the oven to 400 degrees Fahrenheit. Thinly slice the onion and garlic. Melt the butter in a small saucepan over a low heat. Add the onion and garlic, sweating gently for a few minutes until tender and fragrant.
Add the cream cheese to the saucepan. Add the smoked paprika, thyme and rosemary. Stir over a medium heat until the cheese has melted. You may add more herbs and spices as desired.
Add the stock to the saucepan. Stir well to combine, heating through. Add 2/3 of the grated cheddar and the parmesan. Stir well until the cheese has melted into the stock and simmer gently until you have a thick creamy sauce.
Preheat the oven to 400 degrees Fahrenheit. Arrange the cauliflower florets in the base of a medium oven dish. Pour the smoky cheese sauce evenly over the cauliflower florets. Sprinkle over the remaining grated cheese. Transfer to the oven and bake for 18-20 minutes or until golden and bubbling. Serve with your preferred Keto mains.