Mix the sauce ingredients in a small bowl and set aside.

Add the slurry ingredients in a small bowl and stir to mix well.

Heat 1/4 cup water in a large skillet over medium-high heat until hot. When the water starts to boil, add the broccoli and sprinkle with a pinch of salt. Cover the pan and let steam for 1 minute. Uncover the pan and stir until the broccoli is al dente and the water has evaporated. Transfer the broccoli to a big plate.

Wipe the pan clean with paper towels and add 2 tablespoons of the oil. Turn to high heat. Add the mushrooms. Let sear for 1 minute without touching. Then flip the mushrooms, cook and stir occasionally for 2 to 3 minutes, until the mushrooms are browned and there’s no juice left in the pan.

Move the mushrooms to one side of the pan. Pour the remaining 1/2 tablespoon oil on the other side and add the chili peppers, garlic, ginger, and green onion. Stir a few times until the chili pepper turns dark red. Then stir everything together.

Add the broccoli back to the pan. Pour in the sauce. Stir and cook for 30 seconds. Stir the slurry mixture again until the cornstarch is fully dissolved. Swirl into the pan. Cook and stir until the sauce thickens, then transfer everything to a big plate. Serve hot as a side or over steamed rice as a main dish.