Rehydrate dried shiitake: Add dried shiitake and water to a bowl and set aside for a couple hours to rehydrate the shiitake. If you're short on time, use hot boiling water.
Boil tofu (optional): Add tofu to a small pot with water and bring to a boil. Boil for 1 minute, then drain and set aside. Tip: You can skip this step if you're short on time, but it makes the tofu more flavorful and hold together better.
Prep dried shiitake: Set a sieve over a bowl and pour the shiitake in. Squeeze the water out of the rehydrated shiitake and add to the soaking water. Save this water! Chop the shiitake and set aside with the other mushrooms.
Mix seasonings: To the bowl with the leftover shiitake water, add remaining seasonings (miso, sake, soy sauce, vegetarian oyster sauce, spicy doubanjiang, and sesame oil). Mix well and set aside.
Stir fry aromatics, eggplant, and mushrooms: Heat oil in a deep pan or wok over medium heat. Add garlic, ginger, and the white parts of the green onions. Once fragrant (about 30-60 seconds), add eggplant and mushrooms. Cook until the mushrooms have released their liquid and the eggplant is tender.
Add tofu and seasonings: Add tofu and pour in the seasonings. Gently stir so everything is well combined. Simmer for about 2 minutes so tofu heats through.
Thicken with starch slurry: Dissolve cornstarch in 2 tbsp water to make a slurry. Add the slurry and stir to incorporate. Once the sauce thickens, turn off the heat. Top with the green parts of the green onions. Sprinkle sansho on top if using and serve immediately.
Notes
GLUTEN-FREE: Use tamari instead of soy sauce, and check the ingredients for your doubanjiang and vegetarian oyster sauce since some contain wheat. You can use my homemade vegan oyster sauce.1) You can use other varieties of mushrooms depending on what's available to you. 2) Some mapo tofu recipes use soft/silken tofu. I prefer medium firm tofu since it has more of a bite to it but is still soft and bouncy. You can use silken tofu if you prefer, or a mix of both! 3) You can omit the vegetarian oyster sauce and add another 1-2 tsp of soy sauce, or try black bean garlic sauce.