Preheat the oven to 375 degrees. Cook macaroni according to package directions.
Into a blender, add cashews, milk, and tofu, and blend. Add nutritional yeast, mustard, tahini, lemon juice, garlic powder, nutmeg, salt, and black pepper, and blend on high for 3 minutes, scraping down sides of the blender as needed, until the sauce is totally smooth. Set sauce aside.
When macaroni is done, drain and return to the pot. Add sauce and stir to combine. Pour macaroni and cheese into a 13 x 9-inch baking dish and smooth out evenly.
In a small bowl, combine pecans, breadcrumbs, and oil, and toss to coat. Top macaroni and cheese with pecans and breadcrumbs. Bake for 10 to 15 minutes, or until the topping is crispy and brown.