Prep your mise en place: break up clumps of the chilled cooked brown rice with your fingers or a fork into loose grains (this helps the rice separate quickly in the pan and allows more surface to toast). Measure and mince the garlic, dice the onion, thaw the frozen mixed vegetables under cold running water if they're stuck together, and beat the egg lightly with a pinch of salt.

Heat the pan: place a heavy skillet or wok over medium-high heat and add the neutral oil. Bring it until it is shimmering but not smoking — hot oil is essential to quickly sear the rice and vegetables so they stay distinct rather than steaming.

Sauté aromatics: add the diced onion and cook 1–2 minutes until translucent and fragrant, stirring frequently so they soften without browning heavily. Add the minced garlic and cook 20–30 seconds until fragrant—browning garlic burns it and yields bitterness, so keep it brief.

Cook the vegetables: add the mixed vegetables and stir-fry 1–2 minutes until they are heated through and any excess water has evaporated. Cooking off extra moisture prevents the rice from becoming soggy and promotes light toasting.

Make room and cook the egg: push the vegetables to one side of the pan to create a blank hot surface. Add a tiny splash of oil if the pan looks dry, pour in the beaten egg, and let it sit 10–15 seconds to just set. Scramble quickly until just-cooked but still tender — slightly undercooked is fine because it will finish when mixed with the hot rice. Cooking the egg separately then mixing ensures even distribution and silky texture.

Add the rice and sear: add the broken-up brown rice to the pan and spread it out. Let it sit undisturbed 30–45 seconds so individual grains can toast and develop a toasty flavor. Stir and repeat 1–2 times — building those small toasted bits is what gives restaurant fried rice its character.

Season and combine: drizzle the soy sauce evenly around the pan (this helps it evaporate slightly and coat grains rather than puddling). Stir everything so the egg, veggies, and rice combine. Taste and add a small pinch of salt or more soy sauce if needed. If you want a touch of brightness, stir in 1/2 tsp rice vinegar or a few drops of lime juice now.

Finish with sesame oil and rest: remove the pan from the heat and drizzle the toasted sesame oil over the rice — adding it at the end preserves its aroma. Stir to combine. Let the rice sit in the warm pan 1 minute; this lets flavors marry and any remaining steam settle so you don’t end up with soggy rice.

Plate and garnish: transfer to a warm bowl or plate, top with sliced scallion and optional toasted sesame seeds. Serve immediately while hot and slightly crisp.