Trim the bottom inch from each bok choy head to release the individual leaves. For any particularly thick white stems, slice them lengthwise so they'll cook at the same rate as the tender green parts.
Whisk together the garlic, oyster sauce, soy sauce, fish sauce, sweet chili sauce, and brown sugar in a bowl. Keep stirring until the sugar completely dissolves — you want a smooth, glossy sauce with no gritty bits.
Get your wok or largest pan screaming hot over medium-high to high heat. Add the coconut oil and swirl it around to coat the surface. The oil should shimmer and move freely when the pan is properly heated.
Toss in the bok choy along with 2-3 tablespoons of the sauce. Stir-fry vigorously for 1-2 minutes until the liquid starts to evaporate and the pan looks almost dry. This initial searing creates those coveted crispy edges.
⏱ 1 min 30 sec
Keep the heat high and gradually add more sauce, a splash at a time, while continuously stir-frying. The leaves should turn brilliant green and the stems should feel tender-crisp when pierced with a knife. This gradual sauce addition prevents steaming and builds better flavor.
Give it a taste and make adjustments. If it's too tangy, sprinkle in a pinch more brown sugar. Too salty? A squeeze of lime juice balances things out. Want more heat? A dash of chili flakes does the trick.
Slide the bok choy onto your serving platter, then drizzle any remaining sauce from the pan over the top. Serve right away while the stems still have that perfect snap and the leaves are vibrant green.