Soak shiitake mushrooms in hot water for 20 minutes, covered.
Meanwhile, cut and grate the rest of the filling ingredients.
Once shiitake mushrooms have softened and almost doubled in size, gently squeeze out excess liquids (note 3). Cut off and discard the stems and finely dice.
Cook shiitake mushrooms on medium-low heat in a pan with 1 tablespoon of oil until golden and fragrant. About 2 minutes.
Add onions and garlic, stir fry for 2 minutes then add carrots. Turn the heat up to high and stir fry for 2 minutes.
Push ingredients to the rims of the pan, add remaining oil into the middle of the pan then spinach. Continue to cook on high, stir-frying for 4 minutes or until excess liquids have evaporated and you can start to hear the pan sizzle.
Combine cooked vegetables into a large bowl with fresh tofu, soy sauce, sesame oil, salt and pepper. Mix well until tofu is about the same size as the rest of the vegetables. Taste filling and adjust for salt and pepper to taste.