Cut the chicken breasts into bite-sized pieces and pat dry with paper towels. In a mixing bowl, whisk together the sweet chili sauce, soy sauce, minced garlic, and minced ginger. Add the chicken and toss to coat evenly. Cover and refrigerate for at least 30 minutes, or up to 2 hours.

Place the cornstarch in a shallow bowl and season lightly with salt and pepper. Remove the chicken from the marinade using a slotted spoon, letting excess sauce drip back into the bowl. Reserve the marinade. Dredge each piece of chicken in the cornstarch until evenly coated.

Heat the vegetable oil in a large skillet or wok over medium-high heat until shimmering. Add the chicken in a single layer and cook in batches if needed to avoid crowding. Cook for 4 to 5 minutes per side until deep golden brown and cooked through to 165 degrees F.

Transfer the cooked chicken to a paper towel-lined plate. In the same skillet, reduce heat to medium and pour in the reserved marinade. Bring to a simmer and cook for 2 to 3 minutes, stirring often, until slightly thickened.

Add the chicken back into the skillet and toss to coat in the glaze. Cook for another 2 minutes. Taste and adjust heat with sriracha if desired. Transfer to a platter, top with green onions and sesame seeds, and serve hot over rice or noodles.