Whisk Mayonnaise (1/4 cup), Sour Cream (1/4 cup), Fresh Dill (2 tablespoon), Lemon Juice (2 teaspoon), Celery Salt (1/4 teaspoon), and Ground Black Pepper (1 pinch) together in a small bowl and keep chilled until ready to use.
Sprinkle Kohlrabi (2 cup) with Salt (1/2 teaspoon) and allow to sit for 5 minutes. Drain and squeeze dry with a paper towel.
Pat Potato (1 cup) dry with a paper towel. Add to kohlrabi.
In a large bowl, stir together Large Egg (1), Fresh Dill (2 tablespoon), Dijon Mustard (1 teaspoon), Celery Salt (1/4 teaspoon), and Ground Black Pepper (1/4 teaspoon).
Stir in Lump Crab Meat (4 ounce), prepped and dried grated kohlrabi and potato, Breadcrumbs (2 tablespoon), All-Purpose Flour (2 tablespoon), and Scallion (2 stalk).
Add Canola Oil (as needed) to a large nonstick skillet and heat over medium heat until hot. Form approximately 1/4 cup of batter into a 3 or 4-inch round patty. Flatten as much as you can while still retaining its shape.
Pan fry for 5-6 minutes on each side, adjusting heat if necessary. Remove to a paper towel lined plate and keep warm in a low oven while cooking any remaining cakes.
Serve immediately with dill sauce.