Preheat your wok or deep skillet over medium-high heat until shimmering slightly, ready to sizzle.
Add vegetable oil to the hot pan, swirling to coat the surface evenly. When it just begins to shimmer, toss in the minced garlic and stir constantly, cooking for about 20 seconds until fragrant and slightly golden.
Add the sliced mushrooms to the pan, spreading them out in a single layer. Sauté for 2-3 minutes, stirring occasionally, until they turn golden brown and start to release their juices, filling the kitchen with earthy aroma.
Introduce the broccoli florets into the pan, stirring vigorously to coat them with garlic and mushroom juices. Cook for 3-4 minutes, stirring often, until the broccoli brightens to a vibrant green and remains crisp-tender.
Pour the soy sauce over the vegetables and sprinkle chili flakes if using. Stir thoroughly, cooking for another minute until the sauce thickens slightly and clings to the veggies, creating a glossy coating.
Remove the pan from heat and drizzle the sesame oil over the stir-fry. Toss gently to distribute the nutty aroma evenly. Taste and adjust seasoning if needed.
Transfer the hot stir-fry to a serving dish and let sit for a minute to settle. Serve immediately, enjoying the crisp-tender vegetables coated in savory, garlicky sauce with a fragrant finish of sesame oil.
