Whisk together the soy sauce, sake, mirin, sesame oil, ginger, and garlic in a large bowl until evenly combined.

Add the chicken, and toss until every piece is well coated.

Cover tightly with plastic wrap, and refrigerate for at least 4 hours or up to 12 hours.

Remove the chicken from the refrigerator, and let it stand at room temperature for about 10 minutes.

Add the egg white and ½ cup of the potato starch to the chicken in the bowl, and toss until the chicken looks lightly coated and tacky.

Place the remaining 1½ cups potato starch in a shallow dish.

Working with a few pieces at a time, dredge the chicken in the starch, pressing gently so it adheres and shaking off any excess.

Heat the canola oil in a large, heavy-bottomed pot or Dutch oven over medium-high until it registers 320°F.

Working in batches, carefully lower the chicken into the oil, making sure not to overcrowd the pot.

Fry for 3–4 minutes per batch, until the chicken is pale golden and the coating has set and is hardened.

Transfer the chicken to a wire rack set over a baking sheet, and let it rest for 2–3 minutes.

Meanwhile, heat the oil over medium-high until it reaches a temperature of 360°F.

Working in batches, return the chicken to the oil, and fry for an additional 1–2 minutes, until a thermometer inserted into the thickest part of the meat registers 165°F and the chicken turns deep golden brown and crispy.

Return the fried chicken to the wire rack, and season lightly with salt to taste.

Garnish with togarashi, and serve immediately alongside lemon wedges for squeezing.