1. Preheat oven to 425 degrees F. Put the pasta on to cook according to package directions. Puree the cashews in a blender with a splash of water, scraping down the sides when necessary.
2. Add the orange pepper to the blender along with the arrowroot, mustard powder, garlic flakes, and peppercorns. Blend until smooth, adding a little water whenever necessary.
3. Put the oil into a saucepan and warm over medium-low heat, then add the yeast flakes and warm, stirring, until they begin to smell toasty. Do not overheat, they burn easily!
4. Pour in the mixture from the blender and stir frequently until thickened, adding more water bit by bit until the sauce reaches your desired consistency. (Bear in mind that it will thicken a little upon baking.) Salt, to taste.
5. When the pasta is done, drain it and mix with the sauce in a large baking dish. Sprinkle with breadcrumbs and bake until golden on top, about 20 minutes. Devour.
Source of recipe: I experimented, it worked, then I wrote down this recipe.