Slice up the russet potatoes (Leave skins off or peel them up to you), sweet potato (take the skin off), bell pepper, and onions into chunks. Throw into a large cooking pot. Take the skin off of the garlic and measure out the raw cashews and throw them all into the pot. Put water into the pot until all of the ingredients are covered in water (Remember you will be saving about 3 1/2 cups of this liquid after cooking to make the sauce). Allow to boil and then simmer until all the veggies are tender and pierced with a fork. This can take about 30 minutes to an hour since it's such a large quantity. Keep an eye on it.
Place the lemon juice, arrowroot powder, nutritional yeast, tahini, sea salt, smoked paprika, and crushed red pepper in a large blender. Set aside.
Once the vegetables are done cooking, let them cool off a little, so they aren't scalding hot when you place them into your blender. Once a little cooled off, take them out small batches at a time with a slotted spoon and blend in your blender, adding about 1 cup of cooking water each time. I use my Vitamix 3 separate times to blend all of the ingredients due to not fitting everything in there just one time. Then I pour the contents after each blend into a large bowl to mix all ingredients.