Add roasted, peeled and mashed sweet potatoes, raw cashews, water, sea salt, minced garlic, mustard seed, light brown sugar and cayenne pepper to a high speed blender. Blend until smooth, about 7-9 minutes at the highest speed.
In a large bowl, toss sliced mushroom with safflower oil, sea salt, and freshly ground pepper. Allow to marinate for 30 minutes before cooking. Layout shiitake mushrooms in a single layer on a baking sheet and bake for about 30 minutes, until the steam disappears and the shiitakes are evenly browned. When ready, transfer to a paper towel lined dish to drain. The mushrooms will crisp as they cool.
Place the shell pasta in a pot with ¼ water, per cup of pasta. Bring to a boil to reheat the pasta. Add 1/3 cup of sweet potato sauce per cup of pasta and add ½ tablespoon of vegan margarine per cup of pasta. Allow all to cook together and simmer until sauce has thickened and enrobes the pasta. Serve topped with smoked paprika and shiitake bacon.