Peel, devein, and rinse the shrimp under cool water. Drain well and season with salt and black pepper.

Heat 1 tablespoon of vegetable oil in a large frying pan or wok over medium heat. Add the seasoned shrimp and stir-fry for about 2 minutes until they start to turn pink. Remove the shrimp from the pan and set aside.

In the same pan, add the remaining 1 1/2 tablespoons of oil over low heat. Add the sliced onion, garlic, ginger, and stir for about 1 minute to build flavour. Then add the green and red bell peppers. Cook for 3-4 minutes, stirring often, until they begin to soften.

While the vegetables cook, combine the soy sauce, hoisin sauce (if using), sesame oil, and oyster sauce in a small bowl. Mix well.

Turn the heat to medium-low, pour in the sauce mixture, and stir to coat the vegetables evenly. Rinse the sauce bowl with 1 tablespoon of water to capture any remaining sauce and add it to the pan.

Cook for 2 minutes to allow the sauce to thicken slightly. Return the shrimp to the pan, stirring well to coat with the sauce and warm through.

Turn off the heat and sprinkle the sesame seeds and chopped scallions over the stir-fry.

Serve hot with steamed sticky rice or your favourite noodles. Add chili oil or fresh sliced hot peppers if you like it spicy.