Add cashews to a bowl, cover with hot water and let soak for at least 2 hours.
While cashews are soaking, preheat the oven to 425ºF. Chop cauliflower into florets, and peel and chop the potatoes. Arrange on a baking sheet and drizzle with about 1½ tablespoons of oil. Season with salt and pepper.
Cut the top off the garlic bulb so that some of the cloves are slightly exposed. Drizzle with remaining oil and season with salt and pepper. Wrap bulb in tin foil and place on sheet with vegetables.
Roast for 20 – 25 minutes until the cauliflower is starting to brown and the potatoes are soft (they don’t have to be totally soft because we’ll be blending them later). Check the garlic after 15 minutes to make sure it isn’t burning. Allow the veggies to cool slightly then add them to a high powered blender. Squeeze/spoon the garlic out of skin and add it to the blender as well.
Drain and rinse the cashews, adding them to the blender along with the hummus and quinoa. Pour in liquids, miso, nutritional yeast (if using) and additional salt and pepper, and blend on high until smooth and creamy. Taste and adjust seasonings (adding more garlic, salt, pepper, miso or other seasonings) as desired.
Serve warm topped with some of the roasted garlic garnish from the hummus, some chopped parsley and a drizzle of olive oil.