Step 1Prepare the cheese crisps: Heat the oven to 375 degrees. Sprinkle the cheese on a parchment-lined baking sheet and bake until crisp, 12 to 14 minutes. Set aside to cool completely, then break into large uneven pieces to garnish the pasta.
Step 2While the cheese is baking, bring a large pot of salted water to a boil. Add the fettuccine and cook according to the instructions on the package, generally 8 to 10 minutes. Drain and run the pasta under cold water to stop the cooking process. Drain again, and return to the pot, tossing with the oil to keep the pasta from sticking together. Set aside in a warm place.
Step 3Heat a shallow skillet over medium heat. Melt the butter in the skillet, then add the shallots, cooking until softened, about 3 minutes. Remove the shallots using a slotted spoon, leaving the butter in the pan. Set the shallots aside in a small bowl.
Step 4Add the spinach to the skillet and cook over medium heat until just wilted, about 2 minutes, stirring frequently. Remove from heat. Toss the spinach with the fettuccine.
Step 5Prepare the alfredo sauce: In a blender or food processor, combine the almond or soy milk, creamer, cashews, sea salt, black pepper, miso, lemon juice, nutmeg, dry mustard and the cooked shallots. Blend until smooth, about 3 minutes. Transfer to a medium heavy-bottom pot and heat over medium heat until warm, 4 to 6 minutes, stirring frequently. Stir in the arrowroot slurry, whisking until the sauce thickens slightly, then remove from heat.
Step 6To serve, add sauce to fettuccine and spinach and toss to coat. Serve warm with one piece of cheese crisp per serving.