Make the sauce by combining oyster sauce, soy sauce, ½ cup of water, and cornstarch in a bowl.
Cut 1 block of tofu into small bite-sized pieces and place them on paper towels to absorb excess moisture. Sprinkle them with salt.
Heat a wok or sauté pan over medium-high heat and add about ¼ inch of oil.
Shallow-fry the tofu until golden brown and crispy. Transfer to a plate. Remove excess oil from the pan.
Season the shrimp with salt and pepper. Sear them until they turn pink and opaque, about a minute on each side. Transfer to a plate.
Sauté onion and garlic until softened, about 2 minutes. Add tomatoes and cook until they start to caramelize, about 3 minutes. Caramelizing the aromatics is crucial for a flavorful base.
Add the carrots and green beans. Stir-fry for about 2 minutes, until tender-crisp. Season with salt and pepper. Add more oil as needed.
Add the chili peppers and stir-fry for a minute, if you want to reduce the spiciness.
Add the bean sprouts along with the sauce. Keep tossing until slightly wilted, about 3 minutes. The bean sprouts will release more water the longer you cook them.
Add the tofu, shrimp, and scallions. Toss them together. Season with ground pepper as desired. Turn off the heat.
Serve and enjoy!