Preheat the oven to 200°C/180°C fan/400°F/gas mark 6.
Chop the cauliflower into florets and spread them out on a roasting tray along with the whole (unpeeled) garlic cloves. Drizzle with the olive oil and sprinkle with a little salt.
Roast for about 20 minutes until the cauliflower is tender and pale golden.
Meanwhile, bring a large pan of salted water to the boil.
Place the roasted cauliflower in a blender and squeeze in the flesh from the garlic cloves, discarding the skin. Add the nutritional yeast, lemon juice, vegetable stock cube, onion granules, non-dairy milk, salt and a good grinding of pepper.
Blend until the sauce is creamy and smooth. Add a little more non-dairy milk if the sauce is too thick. Taste and add more salt and pepper as needed.
Cook the linguine according to the packet directions then heat the sauce in a saucepan over a low heat. Drain the pasta and toss with the sauce. Serve topped with a sprinkle of fresh parsley.