Combine the sauce ingredients in a bowl, stir and set aside.
Add the mushrooms to a bowl and drizzle with soy sauce. Add the cornstarch and toss to coat evenly. Add more cornstarch as needed so that all of the pieces are lightly coated. Heat some oil in a pan over medium heat. Add the mushrooms and spread into an even layer. Let the mushrooms sit undisturbed until browned on the bottom (approx. 3-5 minutes). Flip* and allow the other side to brown. Remove from the pan.
Place the empty pan back on the stove over medium heat. Add the sesame oil, shallots, garlic, bell peppers and serrano peppers. Cook, stirring frequently, until the veggies become slightly tender (approx. 3-5 minutes). Add the sauce to the pan** and allow it to get bubbly. Add the mushrooms back to the pan and toss to coat.
Remove from the heat and serve over rice with green onion and lime wedges.
*The mushrooms will probably stick together when you flip them because of the cornstarch. Don't worry about it - you can gently break them apart when you add them back to the pan with the sauce.
**It will look like you have a lot of extra sauce. The reason for this is so the rice can absorb the sauce when serving. If you don't plan to serve this with rice, I would reserve 2 tbsp of sauce before adding it to the pan.
Calories: 585kcal, Carbohydrates: 86g, Protein: 11g, Fat: 22g, Saturated Fat: 2g, Polyunsaturated Fat: 7g, Monounsaturated Fat: 12g, Trans Fat: 1g, Sodium: 2400mg, Potassium: 679mg, Fiber: 6g, Sugar: 19g, Iron: 2mg