I mix together garlic, red pepper flakes, ginger, brown sugar, soy sauce, apple juice (or stock), water, bourbon (if using), plum sauce, rice vinegar, and liquid smoke ahead of time. This ensures everything is ready before the chicken goes in.
I heat the olive oil in a skillet over medium-high. If using onion and mushrooms, I sauté them first until they start to soften and caramelize. Meanwhile, I toss the chicken pieces in cornstarch so every piece has a light coating.
Once veggies are golden, I push them aside, add the chicken pieces, and sear until the outsides are lightly browned. Then I pour in the sauce, bring it to a boil, lower to a simmer, cover, and stir occasionally until the chicken is fully cooked and the sauce thickens. If it’s too thin, I remove the lid and let it reduce; if too thick, I add a little water.
If grilling, I grill the chicken first until it develops good char, then chop it. Meanwhile I sauté onions/mushrooms in a pan, add the sauce, reduce it a bit, then add the grilled chicken and toss until everything is warmed through and coated.