When using raw kohlrabi in a salad, it's important to use a mandoline to slice it wafer-thin. This allows you to make the most of its delicate, crunchy texture. The dressing's creamy roasted garlic is an ideal counterpart to the crisp kohlrabi.
Preheat oven to 400 degrees. Remove 1 garlic clove from 1 head, and very finely grate, setting aside 1/8 teaspoon. Wrap remaining heads of garlic in foil, and roast until very soft and golden inside, about 1 hour. Unwrap; let cool.
Meanwhile, whisk together grated garlic, lemon zest and juice, paprika, mustard, 1/2 teaspoon salt, and 1 teaspoon water in a small bowl. Squeeze roasted garlic from skins, and add 2 tablespoons to bowl, reserving remainder for another use. Stir to combine but leave very chunky. Stir in oil (do not completely incorporate).
Shave kohlrabi very thinly on a mandoline. Divide among 4 plates; season with 1/2 teaspoon salt. Spoon dressing over kohlrabi, then top with arugula leaves and almonds.
Using the cruciferous arugula -- instead of baby greens or other lettuce -- gives this salad a spicier flavor that complements the mild sweetness of the kohlrabi.