To prepare the tempeh: Place tempeh on a cutting board, width-wise. Slice tempeh into 1/4 inch-wide strips. Fill a small pot about 2/3 full of water. Add tamari and sliced tempeh. Bring to a boil, then simmer for about 10 minutes. Drain tempeh and reserve water. Lay tempeh pieces in a single layer on a paper towel to dry. To make BBQ sauce: Add all ingredients to a medium bowl and whisk to combine. Taste and adjust seasonings. If it’s too thick, add a little of the tempeh water. Oven method: Preheat oven to 375°F. Line a square casserole dish or baking pan with parchment paper. Pour enough sauce to cover the bottom of the casserole dish. Add tempeh slices in a single layer to the dish and spoon on more BBQ sauce so that each slice is covered. Place dish in the oven and bake for about 20 minutes, flipping pieces about 10 minutes into the baking. Tempeh is done when sauce begins to turn dark brown. Serve on rolls with coleslaw. Store extra BBQ sauce in a covered container in the refrigerator for up to a week. Grill method: set heat/flame to medium and place a grilling tray or piece of foil on the grill. Pour enough sauce to cover the bottom of the casserole dish. Add tempeh slices in a single layer to the dish and spoon on more BBQ sauce so that each slice is covered. Using a fork or tongs, remove tempeh slices from casserole dish and lay in a single layer on the foil or grill pan. Cook for about 15 to 20 minutes, flipping pieces halfway through the cooking time. Tempeh is done when the sauce turns dark brown. Serve on rolls with coleslaw. Store extra BBQ sauce in a covered container in the refrigerator for up to a week.