Heat oil in a large skillet. Add chicken, season with salt and pepper, and sear until lightly browned. Set aside.
In the same pan, sauté sliced onion, red and yellow bell peppers until soft.
Stir in garlic, ginger paste, and Panang curry paste. Cook until fragrant.
Add peanut butter, chicken stock, and coconut milk. Mix well.
Stir in fish sauce, lime juice, and brown sugar. Let simmer for 5 minutes.
Return the chicken to the pan. Simmer until fully cooked.
Add Thai basil leaves and cornflour slurry. Stir gently until the sauce thickens.
Serve hot over boiled jasmine or long-grain rice, garnished with chopped peanuts, scallions, and more Thai basil.