Make the dressing and marinate tempeh: Preheat the oven to 425 degrees F (220 C). Shake dressing ingredients (maple syrup, stone ground mustard, soy sauce, olive oil) in a jar until well combined. Marinate the cubed tempeh in about half of the dressing for about 30 minutes, or just while the oven heats up.
Roast tempeh and sweet potato: Place marinated tempeh (with marinade) on a baking sheet. Add diced sweet potatoes to the other half of the baking sheet. Drizzle sweet potatoes with a little extra olive oil, sprinkle with salt, and roast for 25-30 minutes, or until both are browned and tender.
Toss tempeh with more dressing: When both tempeh and sweet potatoes are browned and roasted, toss the warm tempeh with a little more of the reserved dressing so it soaks up lots of mapley-mustardy flavor.
Get the kale all yummy: Place the cut kale in the same bowl that the marinated tempeh was in to grab onto any leftover marinade. Massage the kale with a little bit more of the dressing and the avocado, so the avocado kind of smashes into the dressing and makes the kale tender and a little bit creamy for 2-3 minutes.
Toss and serve: Toss up the roasted tempeh, sweet potato, massaged kale, and sauerkraut in a big bowl. Add any other extras like quinoa, crispy onions, pecans, apples, or dried cranberries if desired. Serve warm and enjoy!