Coat the chicken. Place the sliced chicken and 2 tablespoons of cornstarch in a ziploc bag; seal and shake to coat.
Cook the chicken. Heat 1 tablespoon vegetable oil in a wok or a large 12-inch skillet set over high heat. Add the chicken to the heated oil in one single layer; season with salt and pepper, and cook for about 6 to 8 minutes or until cooked and browned on all sides. If your skillet isn’t big enough, cook the chicken slices in batches. Remove chicken from the wok/skillet and set aside.
Sauté the veggies. To the same skillet, add remaining oil, broccoli, pepper, and mushrooms; cook for 4 minutes or until the veggies are tender. Stir in garlic and cook for 15 seconds. Add the chicken back to the skillet.
Make the sauce. In the meantime, in a small bowl, whisk together the chicken broth, soy sauce, oyster sauce, rice vinegar, chili paste, cornstarch, and sugar.
Add the sauce to the wok. Pour the sauce over the chicken and veggies and bring to a simmer. Continue to cook for a couple minutes, or until the sauce is thickened.
Serve. Remove from heat. Garnish your Hunan chicken with green onions and sesame seeds, and serve.
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Notes
Vegetable Oil: Don't use olive oil. Choose oils with a high smoke point, like vegetable, peanut, sesame, or canola oil. They can handle the heat and won’t break down.
Sauce: Adjust the consistency of your Hunan sauce as per preference. If it's too thick, a splash of chicken broth or water can help to thin it out; for a thicker sauce, a quick cornstarch slurry does the trick.
Veggie Choices: Feel free to get creative with vegetables. Stick to the classics or toss in your favorites for a personal touch. Just ensure they are cut uniformly for even cooking.
Prep Ahead: Adopt the “mise en place” approach, which translates to "everything in its place." Prepping and measuring all ingredients beforehand ensures a smooth cooking experience, especially for stir-fries.
Hot Pan: A hot pan is essential for that perfect stir-fry. Ensure your wok or pan is heated adequately so that ingredients not only sizzle upon contact but continue to do so as they cook. And don't forget to stir.
To store leftovers, place everything in airtight containers and refrigerate for up to 3 days.