2 tablespoons soy sauce, divided
4 5- to 6-ounce chicken breast cutlets, pounded to an even 1/4-inch thickness
Ground black pepper
3 tablespoons peanut oil, divided
4 medium garlic cloves, finely grated
1 tablespoon finely grated fresh ginger
1/4 teaspoon red pepper flakes
4 scallions, thinly sliced, white and green parts reserved separately
1/2 cup dry sherry
1/3 cup unsalted roasted peanuts, roughly chopped
2 tablespoons salted butter, cut into 2 pieces
In a medium bowl, combine 1 tablespoon soy sauce and the chicken, turning to coat. Let stand for 10 minutes. Pat the cutlets dry with paper towels, then season with pepper.
In a nonstick 12-inch skillet over medium-high, heat 2 tablespoons of oil until shimmering.
Add the chicken in a single layer and cook until well browned on both sides, 4 to 6 minutes total, flipping once halfway through. Transfer to a platter and tent with foil to keep warm.
Allow the pan to cool for a couple minutes, then add the remaining 1 tablespoon oil, the garlic, ginger, pepper flakes and scallion whites. Cook over medium, stirring, until the mixture is fragrant, about 30 seconds.
Off heat, add the sherry, the remaining 1 tablespoon soy sauce, half the peanuts and any accumulated juices from the chicken.
Return to medium and cook, scraping up any browned bits, until the sauce is slightly thickened, about 1 minute. Off heat, add the butter and stir until fully incorporated. Pour the sauce over the chicken, then sprinkle with scallion greens and the remaining peanuts.