Preheat the oven to 425°F.
Roast potatoes: Rub the potatoes with olive oil, and salt. Roast for about 60 minutes, or until fork tender.
Simmer the tempeh: Place the tempeh into a medium saucepan with enough water to cover by about 2-inches high. Bring the water to a gentle boil before reducing the heat to low. Simmer for 3 minutes. Drain the tempeh and set aside until cool enough to handle. Dry the tempeh with paper towel. Slice into ¼-inch-thick rectangles, about 1 ½-inches by 2 inches.
Prepare the sauce: In a small bowl, mix the tamari, maple syrup, garlic powder, smoked paprika, and black pepper.
Cook the tempeh: Add 1 tablespoon olive oil to a large nonstick skillet. Heat over medium-high heat. Once the oil starts to shimmer, place the tempeh in a single layer and cook for about 3 minutes on each side, or until both sides of the rectangles are browned. Add 1 tablespoon water to the skillet. Add the sauce and swirl to spread the sauce evenly. Flip the tempeh so both sides are coated in the sauce. Cook each side for 2 to 3 minutes, until there is no more sauce remaining and both sides are browned. Cut the tempeh into about ¼-inch squares. Set aside.
Assemble: Once the potatoes are cooked, slice in half lengthwise and brush both sides with olive oil. Sprinkle with salt and black pepper. Broil for about 4 minutes on each side, or until browned. Top with vegan cheese, and tempeh bacon squares. Broil for another 2 minutes, or until the cheese is melted. Top with vegan sour cream and chives.