Cut off the tough outer skin of the kohlrabi using a large sharp knife and cutting board. Begin by slicing off the top and bottom, then cut of the side in small pieces, angling the knife along the side of the kohlrabi.
Slice the kohlrabi into roughly ¼ inch slices and cut them into matchsticks. Set in a large bowl.
Wash the carrots and peel the outer layer with a vegetable peeler if desired. Using a julienne peeler and the cutting board, julienne the carrots. Place the pieces in the bowl with the kohlrabi.
Wash the kale leaves, then remove the stems by pulling the leaves off. Discard the stems, then pile the kale leaves together and chop into small slivers using the cutting board and large sharp knife. Place the kale slivers in the bowl with the carrots and kohlrabi.
Dressing
Remove the pit from the date and using the cutting board and knife, chop the date into small pieces. Put the date pieces in a single layer in a small, microwavable bowl.
Pour ¼ cup of water over the dates, making sure all the pieces are covered. Microwave the dates and water for 3 minutes, checking every so often to make sure the mixture isn’t bubbling over the sides of the bowl.
Once done, remove the bowl from the microwave (carefully if it’s hot) and use a fork to mash up the dates and remaining water. Keep mashing until the large chunks are gone and a thick paste is formed.
Measure out the mayonnaise, apple cider, vinegar, and kosher salt with measuring cups and spoons and add it to the date mixture. Combine everything with a small whisk or fork until thoroughly mixed.
Pour ⅓ of the dressing into the bowl with the slaw ingredients. Mix it together well with a pair of tongs or a wooden spoon. If you like less dressing, stop here. If you like more dressing, pour a little more in until you reach the desired consistency. If you have any remaining dressing it will keep in the fridge for several days, as will the coleslaw.