1. In the same pan used for the cashews, working in batches if needed, add the chicken and cook over medium-high heat, stirring occasionally, until browned but not yet cooked through, 2 to 3 minutes. Transfer to a plate. Add more oil between batches if needed. Wipe out the pan.
2. In the same pan over medium-high heat, warm 1 to 2 teaspoons (2 to 4 tsp) oil until hot but not smoking. Add as many peppercorns and Chinese chiles as you like and cook, stirring often, until lightly browned, 1 to 2 minutes. Stir in the bell pepper and scallion pieces, season lightly with salt and pepper, and cook until lightly charred, 1 to 2 minutes.
3. Stir in the chicken and any accumulated juices and the gong bao sauce base, toss to coat, and cook until the sauce is thickened slightly and the chicken is cooked through, 1 to 2 minutes.
4. Remove from the heat and discard the chiles, if using. Stir in the cashews and season to taste with salt and pepper.