Press the tofu to remove excess moisture, then cut it into small cubes.

Heat the vegetable oil in a large skillet or wok over medium-high heat.

Add the tofu cubes and fry for 4-5 minutes, turning occasionally, until golden brown. Remove the tofu and set aside.

In the same skillet, add the sesame oil. Stir in the garlic and ginger, cooking for 30 seconds until fragrant.

Add the sliced mushrooms to the skillet and sauté for 4-5 minutes until softened and lightly browned.

In a small bowl, mix the soy sauce, oyster sauce, sugar, black pepper, and water. Pour this sauce mixture into the skillet with the mushrooms.

Return the cooked tofu to the skillet and stir to coat everything evenly with the sauce.

Add the cornstarch slurry (cornstarch mixed with water) to the skillet and stir for 1-2 minutes, allowing the sauce to thicken slightly.

Sprinkle the stir-fry with sliced green onions and optional sesame seeds for garnish.

Serve immediately with steamed rice or noodles.