Combine the rinsed jasmine rice, cold water, and 0.5 teaspoon kosher salt in a medium saucepan. Bring to a boil over high heat, then immediately reduce to the lowest possible setting, cover tightly, and cook for exactly 15 minutes. Remove from heat and let the rice steam, still covered, for 10 minutes. The grains should be fully swollen and separate cleanly when fluffed with a fork.
Pat the chicken thighs completely dry with paper towels. Press them gently to flatten any thick sections so the surface makes full contact with the pan. Season both sides evenly with kosher salt and black pepper. Dry surface = better sear; any residual moisture will cause the chicken to steam rather than brown.
Whisk together the soy sauce, rice vinegar, honey, toasted sesame oil, minced garlic, grated ginger, and the cornstarch slurry in a small bowl. Set it next to the stove. The cornstarch is what gives the finished sauce body and helps it cling to the chicken instead of pooling at the bottom of the bowl.
Heat the skillet over medium-high heat until the oil just begins to shimmer, about 2 minutes. Lay the chicken thighs smooth-side down and press lightly with a spatula to keep full surface contact. Sear undisturbed at medium-high heat for 6 minutes, until a deep mahogany crust releases from the pan without sticking. Flip and cook the second side for 5 minutes at the same heat.
Insert an instant-read thermometer into the thickest part of the largest thigh. Pull the chicken at 74°C / 165°F. Transfer the cooked thighs to a cutting board and tent loosely with foil while the sauce goes into the pan.
Pour the soy-ginger mixture into the hot skillet and scrape up the fond with a wooden spoon or silicone spatula. The sauce will bubble immediately. Cook over medium heat for 90 seconds, stirring constantly, until the sauce thickens enough to coat the back of a spoon. It should look glossy and hold a line when you drag a finger across the spoon.
Slice the rested chicken thighs crosswise into 1.5 cm strips. Return the slices to the skillet off the heat and toss to coat them thoroughly in the pan sauce. Every surface of the chicken should be lacquered and glistening before it goes over the rice.
Divide the cooked jasmine rice evenly among four bowls. Arrange the glazed chicken slices over the rice and spoon any remaining pan sauce on top. Finish each bowl with sliced scallions, toasted sesame seeds, and a drizzle of sriracha if using. Serve immediately.
