Prep: Preheat your oven to 400 degrees Fahrenheit (200 degrees Celsius) and line a rimmed baking tray with parchment paper or a silicone baking mat.
Chop cruciferous vegetables: Chop your washed and dried or spun (I use a salad spinner) kale, cabbage, and arugula first so they can work their sulforaphane magic. I now chop my greens and cabbage using a mezzaluna knife and wooden bowl from Holland Boll Mill, but if you don't have one of those, a knife and chopping board will work just fine.
Massage the greens: This is an optional step, but it does make the kale more palatable if you're not a fan. Add a tablespoon or two of a balsamic vinegar you enjoy to the greens and massage them with your hands for 3 minutes, making sure to really work the fibers of the greens (it's fine if you already mixed the greens and cabbage together). Concentrate on the fibers of the kale, this will help soften it and make it less bitter and hard to chew. Since I chop my kale pretty finely, I no longer take this step, but it was THE thing that helped me learn to enjoy kale, and it's now my favorite leafy green!
Prep sweet potatoes: Wash and dice your sweet potatoes in a small 1/2-inch dice. No need to peel them, there's a lot of nutrition in sweet potato skin! Add the diced sweet potatoes to your lined baking tray. Place them on the center rack of your oven and bake for 20-25 minutes. Note that how long they take to bake depends on the strength of your oven, how small you cut the sweet potatoes, etc. So you may want to check them earlier. Sweet potatoes are done when a fork easily pierces one of the cubes.
Chop remaining vegetables: While your sweet potatoes cook, you can chop your remaining vegetables. I like to dice most vegetables, though I have a few I do something different to. Carrots I usually peel and grate with a box grater. Grape tomatoes (or cherry tomatoes) I usually halve or quarter depending on their size.
Make the dressing: In a bowl, jar, or measuring cup (I always make dressings in a glass measuring cup because I watched my mom do it when I was growing up!), add the hummus, vinegar, and Dijon mustard. Whisk to combine with a small whisk or a fork. Thin it out with cold filtered water. Start with a little, whisk, and add more if needed until you reach the desired consistency. Add in any other flavorings you like, more vinegar, maple syrup or date paste, etc. Whatever you like! I added in dried oregano (thyme is also great) and fresh cracked black pepper.
Dress the salad: When the sweet potatoes are almost done (or done) and you're ready to serve, add the dressing to the salad and toss well with salad tongs or forks. Toss until all the salad looks dressed. Taste and adjust if necessary.
Complete the salad: I like to divide my salad before I add my starches so I can control how much starch I get and how much my partner gets (as they eat more than I do). I measure out my portion of the sweet potatoes (about ¼ to ⅓ of the pan), and my portion of kidney beans (about ½ a cup). I also do only two walnuts for myself and 5 for my partner since they can eat more fat grams than I can and still lose weight! Yeesh!
Serve: Since the salad is dressed, I recommend serving immediately. If you don't want to eat the salad right away, I wouldn't dress it until I was ready to serve it.