Bring a large pot of water to a boil. Add in a big pinch of salt and the potatoes, carrots, and cashews. Boil until tender, about 10-15 minutes. Reserve 1/2 cup of the cooking water and set aside. Strain the potatoes, carrots, and cashews and add to a high-speed blender.
Add the remaining cheese sauce ingredients and the 1/2 cup of reserved water. Blend until smooth. Set aside.
While the potatoes, carrots, and cashews are simmering, add the oil to a large skillet over medium-high heat. Add in the tempeh and seasonings. Continue to sauté, stirring often, until the tempeh gets crispy around the edges. Remove from the heat and set aside.
Preheat the oven to 350 degrees. Lay the tortillas out on baking sheets and toast them in the oven until they are golden brown around the edges, about 15-20 minutes.
While the tortillas are baking, heat the refried beans.
Spread half of the tortillas with refried beans and sprinkle with the taco meat. Place the remaining tortillas on top. Spread the top tortilla with salsa, and then the cheese sauce. Top with olives, tomatoes, and scallions. Serve.