Preheat the oven to 425 degrees and line a large baking sheet with parchment paper.
In a large mixing bowl, toss the cauliflower, starch, avocado oil, and a pinch of salt and pepper until fully incorporated.
Spread the cauliflower onto the baking sheet evenly. Roast for about 15 minutes until tender, then broil for about 2-3 minutes to char a bit.
While the cauliflower roasts, make the cashew sauce by combining all of the cashew cheese ingredients into a high speed blender. Blend on high, about 1-2 minutes until completely smooth. Pour into a small saucepan and bring to a light simmer then remove from the heat.
To assemble the tacos, heat the tortillas if desired. Place mixed greens, roasted cauliflower, drizzle of cashew cheese, crispy onion straws, and cilantro on top to serve.