Step 1: Prepare the Ingredients

1. Clean the Shrimp: Pat the shrimp dry with paper towels and season lightly with salt and pepper.
2. Slice the Vegetables: Cut the bell peppers into thin strips and slice the onion thinly. Mince the garlic and ginger.
3. Mix the Sauce: In a small bowl, whisk together the soy sauce, oyster sauce, hoisin sauce, rice vinegar, sesame oil, and red pepper flakes (if using).

Step 2: Sear the Shrimp

1. Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat.
2. Add the shrimp in a single layer and cook for 1-2 minutes per side, or until pink and opaque. Remove the shrimp from the pan and set aside.

Step 3: Sauté the Vegetables

1. In the same skillet, add the remaining tablespoon of oil.
2. Add the onion, garlic, and ginger, and sauté for 1 minute, or until fragrant.
3. Add the bell peppers and stir-fry for 3-4 minutes, or until they are tender-crisp but still vibrant in color.

Step 4: Make the Sauce and Combine

1. Return the shrimp to the skillet.
2. Pour the prepared sauce over the shrimp and vegetables. Stir well to coat everything evenly.
3. Add the cornstarch slurry and stir until the sauce thickens, about 1-2 minutes.

Step 5: Garnish and Serve

1. Remove the stir-fry from heat and garnish with sesame seeds, sliced green onions, or fresh cilantro.
2. Serve immediately over steamed rice, noodles, or your favorite side dish.