Add the olive oil, lemon juice, apple cider vinegar, Dijon mustard, finely chopped mint, and honey into a small bowl, whisk until combined, season with salt and pepper.
Peel the kohlrabi and cut into thin slices. Stack the slices and cut them into thin matchsticks.
Cut the apple into quarters, cut out the core, cut each quarter into slices and then into matchsticks.
Add the kohlrabi and apple into a large bowl, pour the sauce over. Toss all the ingredients until evenly coated.
Season the slaw with more salt and pepper if necessary, adjust the seasonings if necessary - if the salad is not sour enough add more apple cider vinegar and if it's too sour add some more honey.