Prepare the tempeh: Remove tempeh from packages, cut each in half and steam for 10 minutes. Slice into small triangles or cubes once cool enough to handle.
Make the marinade: In a shallow dish (such as a 9x13 inch dish) add the balsamic vinegar, maple syrup, soy sauce, garlic and olive oil. Whisk right in the dish to combine.
Marinate tempeh: Add the sliced tempeh to the dish and toss to coat each piece in the marinade. Cover and let the tempeh marinate for at least an hour in the refrigerator and up to 24 hours for more flavor. The longer you let it sit, the more flavorful it will be.
Bake: Preheat the oven to 350 degrees F and line a baking sheet with parchment paper. Transfer the marinated tempeh to the baking sheet. Don't throw away the marinade, you will use it. Bake for 25-30 minutes, brushing with more marinade halfway through cooking for extra flavor.
Remove from the oven and brush with even more marinade, if desired for more flavor. Serve and enjoy!
To pan fry instead: Heat a few tablespoons of olive oil over medium-high heat in a large non-stick or cast iron skillet. Add the tempeh pieces, leaving the extra marinade in the dish for now. Cook until a little golden brown on each side, flipping often with a spatula. Add a little extra marinade to the pan and toss the tempeh in it for more flavor.
To air fry instead: Air fry at 400 degrees for 15-20 minutes, shaking occasionally until golden brown. Brush with a little leftover marinade once done cooking, then serve.