for the fries
3 kohlrabi roots with stems removed (if they come with them)
2 tablespoons olive oil
sea salt or kosher salt
chili powder and ground cumin (optional)
for the aioli
4 large egg yolk
6 teaspoons fresh lemon juice
1 1/2 teaspoon Dijon mustard
3/4 cup extra-virgin olive oil
1/4 cup vegetable oil
1 medium head of garlic
1 tablespoon olive oil
Prepare your aioli. This can be done up to two days in advance and kept refrigerated. Cut off and discard tops of garlic head to expose cloves, then brush head with 1/2 tablespoon oil. Wrap in foil and bake in a 400F oven until tender, about 45 minutes. Cool to room temperature. Squeeze garlic from skins into a food processor and purée.
Whisk together yolk, lemon juice, and mustard in a bowl. Combine oils and add, a few drops at a time, to yolk mixture, whisking constantly, until all oil is incorporated and mixture is emulsified. (If mixture separates, stop adding oil and continue whisking until mixture comes together, then resume adding oil.) If aioli is too thick, whisk in 1 or 2 drops of water. Add in the roasted garlic and chopped tarragon. Chill, covered, until ready to use. Let sit a minimum of 30 minutes to let flavors meld.
To make your fries, preheat oven to 425F. Line a baking sheet with parchment paper or silpat.
Peel the kohlrabi with a small paring knife. It’s not necessarily easy, and can’t be don’t with a vegetable peeler, so just work slowly, removing at little of the skin as possible. Cut the kohlrabi into “fry-sized” sticks. First, cut the root in half and then with each half, cut the sticks. Toss kohlrabi with a generous pinch of salt and the olive oil in a bowl and place on a baking sheet. If you want to make them “spicier”, sprinkle with lots of chili powder (basically until they look pretty well covered) and a smaller amount of ground cumin. Bake for 30 minutes, flipping or shaking around once in the middle. Serve immediately with the aioli or with ketchup.