Wash the mixed greens thoroughly in cold water to remove grit. Shake off excess water and spin dry or pat with towels. Trim tough stems: if using bok choy or choy sum, separate leaves from thick lower stems and cut larger stems diagonally into 1/2-inch slices.

Mince aromatics

Peel and thinly slice or mince the garlic. Peel and mince the ginger. Trim scallions and slice into 1-inch pieces, separating whites from greens. If using chili, slice thinly across the length (remove seeds for less heat).

Make sauce

In a small bowl, combine light soy sauce, oyster (or mushroom) sauce, rice vinegar, sesame oil, sugar or honey, warm stock or water, salt, and pepper. Stir until sugar dissolves. Set aside.

Cooking

Heat wok or skillet

Place a wok or large skillet over high heat until very hot (about 2–3 minutes). Add the neutral cooking oil and swirl to coat. The oil should shimmer but not smoke heavily.

Sear aromatics

Add the garlic, ginger, and the white parts of the scallions to the hot oil. Stir-fry for 20–30 seconds until fragrant and just starting to color. If using chili, add it now.

Cook the stems first

Add the thicker stems (if any) to the wok and stir-fry for 30–45 seconds to begin softening. Toss constantly so they don't burn.

Add leaves and sauce

Add the leafy parts of the greens and the scallion greens to the wok. Pour the prepared sauce around the edge. Stir-fry briskly, tossing and flipping the leaves so they wilt evenly. If the pan looks dry or the greens are large, add the remaining 1–2 tablespoons of stock or water to help steam and evenly cook.

Finish and adjust seasoning

Continue stir-frying for 1–2 minutes until the greens are tender-crisp and bright green. Taste and adjust with a pinch more salt or a splash more soy if desired. Remove from heat and drizzle the finishing sesame oil over the greens, tossing gently.

Serve

Transfer to a serving plate, sprinkle toasted sesame seeds if using, and serve immediately as a side dish or over steamed rice.