Preheat the oven to 190c.
Peel the carrot and potato and chop them into small chunks, then peel the skin off and quarter the onion and slice the top off the garlic bulb.
Add everything to a roasting tray, drizzle with oil, season, and roast for 30–40 minutes until soft and lightly golden.
Once the veg is out of the oven, squeeze the roasted garlic cloves out of their skins and add them to a blender with the carrot, potato and onion.
Add the nutritional yeast, cashews, the juice of half the lemon (you can add more later), Dijon mustard, vegan butter, miso paste and oat milk.
Blend until completely smooth and glossy.
Taste and adjust with more lemon if needed.
Season well.
Bring a large pan of salted water to the boil and cook the pasta until just al dente.
Scoop out about a cup of the pasta water, then drain.
Add the pasta back to the pan on a low heat, pour over the sauce and loosen with the reserved pasta water until it’s saucy and coats everything nicely.
Let it bubble gently for a minute or two to thicken.
Season well, then serve.
