Meanwhile, bring a medium pot of water to a boil. Add the cauliflower florets to the pot and boil for 7 minutes or until very fork-tender. Strain off the water.
Add the boiled cauliflower florets, 1 cup of the plant-based milk, cashews, nutritional yeast, lemon juice, apple cider vinegar, sea salt, and black pepper to a high-speed blender (do not use a food processor).
Blend on high for 2 minutes or until completely smooth and creamy. Set within reach of the stove.
Heat a large pan over high heat. Once the pan is hot, add the mushrooms, reduce heat to medium-high, and cook for 4 minutes, or until tender, nudging them around the pan as needed to prevent burning. It will initially seem like the mushrooms might burn but this is about the point when they will release their liquid. Continue cooking until there is just the tiniest amount of mushroom liquid remaining in the pan and the mushrooms have a deep golden-brown glisten to them.
Then, reduce heat to medium-low and add the garlic and olive oil. Continue to cook for another 2 minutes, or until the garlic mellows and softens, stirring frequently.
Stir in the cauliflower sauce, increase the heat to medium, and simmer for 1 minute, or until hot and bubbly.
Turn off the heat, add the pasta to the pan, and toss to coat. If a slightly thinner sauce is desired, add more plant-based milk, one small splash at a time, to thin (I usually add another ¼ to ½ cup). (Note: If you add more milk, you'll need to increase the seasoning to accommodate.)
Taste and generously season with more sea salt and black pepper to taste.