Toss the cabbages and carrot with 1 teaspoon salt in a colander set over a bowl or in the sink; let it stand until the cabbage wilts, which will take between 1 to 4 hours.
Rinse the cabbage under cold running water (if you're serving the slaw immediately, rinse under water and then in a large bowl of ice water to chill).
Press gently to drain then pat dry with paper towels; cabbage can be stored overnight in refrigerator to chill in a re-sealable container.
To make the dressing, in a food processor purée together the peanut butter, oil, vinegar, soy sauce, lime juice, brown sugar, garlic, ginger, cayenne, and jalapeno (if using) until smooth (taste it at this point to see if you want to add more cayenne or jalapeno).
Toss the dressing with the cabbage, carrot, grated kohlrabi, water chestnuts, and green onions (and the currants, if using - they add nice little surprising bits of sweetness to the slaw!) together in a bowl.
Season with salt and pepper, to taste.
Cover, and refrigerate until chilled and ready to serve; garnish with sesame seeds.
Makes about 6 cups, serving 6 to 8.
Note: you can also make the slaw without wilting the cabbage/carrot in the 1 tsp of salt - it's up to you. You might try it both ways to see which you prefer.