Roasting and grilling: Preheat the oven to 350 degrees F. Take the half-head of green cabbage and cut into thick slices. Add to a large bowl and separate the leaves (you'll have about 2 cups). Trim and halve the Brussels sprouts and add them to the bowl. Toss the green cabbage and Brussels sprouts with olive oil and salt until the vegetables are completely coated. Place on a baking sheet lined with parchment paper and roast until they are browned and nicely caramelized, 20-25 minutes. Remove from oven and let cool. Meanwhile, preheat a grill pan to high heat. Grill 1 pickled cabbage leaf for about 1 minute, being sure to grill both sides. Remove, finely chop, and set aside.
Assemble the salad, part 1: If there are any flowers among your Asian greens, remove them and reserve for garnish. Thinly slice the greens and set aside in a bowl, about ½ cup. Stack mint leaves, thinly slice, and add to the greens, about 2 tablespoons. Peel the kohlrabi with a knife, then use the spiralizer (on the smallest setting) to make 2 cups of kohlrabi “noodles.” Add to the bowl and mix together with the mint, Asian greens, and ¼ cup of the Walnut Dressing.
Supreme the oranges: Cut off the top and bottom of the orange. Set it down on its bottom and use your knife to slice off the peel completely. Then carefully slice out each individual segment by running your knife as close possible to the membranes separating them. Repeat with the second orange. Set the supremes aside. Assemble the salad, part 2: Place the roasted cabbage and Brussels sprouts into a large bowl; add the pickled cabbage pieces, another ½ cup of the dressing, and toss well to coat. Serve by placing the roasted vegetables into a bowl or serving platter, making a little "nest" for the other ingredients. Finally, add the cabbage noodles and arrange the orange supremes on top. Add a sprinkle of salt, the reserved flowers if you have them, and serve.
Place cabbage leaves in a large, nonreactive baking dish. Add salt to the vinegar to taste (it should taste like salt and vinegar potato chips); then pour over the cabbage. Press the leaves down to absorb the liquid and set aside to pickle for 1 hour; when the leaves are limp, having released much of their water, they're ready to absorb the marinade. In a blender, combine the ginger, garlic, and olive oil, then pout it on top of the cabbage. Finally, add the orange juice and crushed red pepper flakes, them massage the marinade into the cabbage to distribute thoroughly. Let rest at room temperature for 2 hours. (Pickled Cabbage will keep in a covered container, submerged in pickling liquid, in the refrigerator for several weeks.)
In a blender, pulse the walnuts and water for a few seconds to combine. Then add the garlic, ginger, orange juice, tamari, rice vinegar, lemon peel, and lemon juice. Blend until smooth. Add Tabasco, taste to adjust seasonings, and set aside. (Dressing will keep in a covered container in the refrigerator for several weeks.)