For the dressing: In a small bowl, combine the garlic, lemon juice, Dijon mustard, and Worcestershire sauce. Add the mayonnaise, Parmesan, salt, and pepper, and stir until combined. At this point, I add a drizzle of water to thin just a bit. This will make the dressing easier to evenly distribute throughout the kale. Alternatively, if your kale is still damp from washing, the little bit of water clinging to the leaves will accomplish the same thing. No need to add water in that case. Make-ahead tip: The dressing may be prepared in advance and will keep well in the fridge for about a week.
Place the slivered kale and optional tomatoes and/or scallions in a large salad bowl and toss with dressing. Start with about half of it, toss well, and then add more to taste. (Tip: Keep tossing to make sure the greens are evenly coated and there are no clumps of unmixed dressing lurking. Go lighter than you think at first and add more as needed.) If time allows, refrigerate for an hour or so to allow the flavors to meld and the kale to soften slightly. Top with any of the other optional ingredients, as desired, and enjoy.
Storage: Leftovers will keep, tightly covered, for up to 5 days. If expecting leftovers, I don't stir in any crunchy additions like croutons, but instead use them as a topping. Any remaining dressing may be saved for upwards of 2 weeks and used for future salads. Or add more greens—whether more kale, romaine, shaved Brussels sprouts, spinach, or cabbage—to the leftovers to make use of any remaining dressing.
Notes
*Best way to prepare the kale? Strip the leaves away from the tough stems, and then stack the leaves and roll into a tight “cigar” (you can fold over the skinnier ends before rolling), and then slice very thinly (⅛- to ¼-inch wide) with a sharp knife.