2 leeks, white and light green parts only, sliced ¾ inch thick
1 cup all-purpose flour
1 teaspoon baking powder
½ teaspoon ground cumin
¼ teaspoon ground coriander
¼ teaspoon ground caraway
¾ cup whole milk
1 cup grapeseed or other neutral oil, plus more as needed
Soak the leek disks in water for 20 minutes, lightly swishing them in the water with your hands. Drain the water and repeat once more. Drain and lay the leek disks on a kitchen towel or paper towels to dry.
In a large bowl, whisk together the flour, baking powder, cumin, coriander, and caraway. Whisk in the milk and add soda water as needed: the consistency should be smooth and like that of thick pancake batter. Stir in the leeks. Refrigerate for 20 minutes.
In a large cast-iron pan, bring the 1 cup of grapeseed oil up to 350°F over medium-high heat. Drop 2-tablespoon dollops of leek batter into the hot oil and shallow-fry, flipping the fritters over if they’re not completely submerged in the oil, until golden brown, 3 to 4 minutes.
Transfer to paper towels to drain and season with salt immediately.