Heat 1 to 2 tablespoons oil in a wok or large saute pan over medium-high heat until it shimmers. Add the pork and cook, in batches if necessary, until the pork is lightly browned and cooked through. Transfer to a plate and set aside.
Add the onion to the wok or pan and cook, stirring, for 3 to 4 minutes, until soft and lightly browned. Transfer to a bowl and set aside.
Reduce the heat to medium; add the mushrooms and cook, stirring, for 3 to 4 minutes, until they have exuded their liquid. Transfer to the bowl with the onions and set aside.
Add the celery to the wok or pan, adding the remaining oil as necessary, and cook, stirring, for 3 to 4 minutes, just until crisp-tender. Transfer to the bowl with the onions and mushrooms.
Over medium heat, return the pork to the wok or pan; add 1 1/2 cups chicken broth and use a spatula to dislodge any browned bits from the bottom of the pan.
Add the soy sauce, brown sugar, brown gravy, and salt and pepper to taste. Increase the heat to medium-high and cook, stirring, until the sauce begins to bubble at the edges. Add the cooked vegetable mixture, stirring to combine; cook for 3 to 4 minute. Taste and adjust the seasoning.
In a small bowl, combine the cornstarch and remaining 1/4 cup chicken broth, mixing well to combine. Add the cornstarch mixture, stirring constantly until the gravy is thickened.
The Substitution Factor
Swapping ground pork for thinly sliced shoulder changes the moisture release entirely during browning, demanding careful temperature management over medium-high heat. When proteins crowd the pan, they steam rather than sear, which leaves the foundational meat gray instead of richly browned. Monitoring the wok until the oil shimmers at roughly 375 degrees Fahrenheit prevents this common saturation error.
Accompaniments and Texture
Pairing this savory, broth-based stir-fry requires a canvas that absorbs liquid without disintegrating into mush. Steamed jasmine rice or fried noodles must offer structural resistance against the cornstarch-thickened gravy, balancing the dominant notes of soy and pepper. Without a starchy base to anchor the dish, the sodium content overwhelms the palate within three distinct bites.
Equipment Realities
Traditional carbon steel woks distribute heat rapidly, but domestic flat-bottomed skillets serve as viable alternatives if preheated for five full minutes. Overcrowding these smaller surfaces causes the mushrooms to stew in their own juices instead of developing deep caramelization. Working in small batches guarantees that celery retains its crisp-tender bite rather than turning limp.