Prep time: 20 minutes, plus 2 hours marinating
Total time: 3 hours
for the Karaage:
2 tablespoons kosher salt
8 boneless chicken thighs, cut in thirds (about 1 pound|450 grams)
4 cups|1 liter cooking sake
2 cups|500 ml soy sauce
1 (2-inch) piece ginger
6 garlic cloves
2 cups|300 grams potato starch
Vegetable oil, for frying
for the Japanese tartare sauce:
5 large eggs
1 cup|180 grams diced pickles
1/2 cup|160 grams kewpie mayonnaise
1 teaspoon freshly ground black pepper
12 slider potato rolls
½ head iceberg lettuce, shredded
1. Brine and marinate the chicken: In a medium saucepan, bring 4 cups water to a boil. Add the salt and cook until dissolved, then cool completely. Add the chicken and refrigerate for at least 1 hour and up to 4 hours.
2. Meanwhile, place the sake, soy sauce, garlic, and ginger in the bowl of a blender and purée until smooth.
3. Drain the chicken, discarding the brine, and place the chicken and the marinade in a bowl. Cover and refrigerate for 1 hour more.
4. Meanwhile, make the tartare sauce: Bring a medium saucepan of water to a boil. Add the eggs and cook for 10 minutes, then transfer to an ice bath. Drain the eggs, then peel and dice them. Place in a bowl with the remaining ingredients, cover, and refrigerate until ready to use.
5. Heat 3-inches of vegetable oil in a large saucepan until a deep-fry thermometer reaches 295°F. Add 1/2 cup of potato starch to the chicken marinade to create a slurry. Place the remaining potato starch in a medium bowl and lightly dish the chicken in the flour, dusting off any excess. Working in batches, fry the chicken until golden brown, 3 minutes. Transfer to a rack fitted over a baking sheet and repeat with the remaining chicken.
6. To assemble the sandwiches, place a piece of chicken in each roll along with some tartare sauce and lettuce. Skewer to help hold it together and serve immediately.