In a large bowl or resealable plastic bag, add the chicken pieces and season with salt and pepper. Add 1 cup of the potato starch and toss to coat each piece. Remove the chicken pieces and repeat. Add the pieces to the bowl or bag, sprinkle in the remaining 1 cup potato starch and toss to coat each piece again. Set aside on a plate until the starch on the chicken begins to look wet, about 15 minutes.

Pour 2 inches oil (enough to cover the chicken pieces while frying) into a large Dutch oven. Heat over medium-high heat to 350°F.

Line a plate with paper towels. Working in batches of a few pieces at a time, add the chicken to the hot oil and fry until lightly golden, about 4 minutes per batch. Transfer the fried chicken to the paper towels. Then, fry these same pieces a second time until golden brown, about 8 minutes per batch. Set these twice-fried chicken pieces aside on a wire rack until you’ve double-fried all of the chicken.

In a medium skillet, combine ½ cup vegetable oil, the garlic, 2 of the jalapeños, the brown sugar, and soy sauce and set over medium-high heat until it bubbles up. Add a few pieces of the fried chicken to the sauce and use tongs to quickly turn them over in the glaze just until coated. Remove and transfer to a serving platter. Repeat with the remaining chicken.

Garnish the fried chicken with the remaining jalapeño slices and serve immediately or at room temperature, when the soy sauce glaze on the outside will be at its crunchiest.