Rinse and cook the jasmine rice: Rinse 1 cup jasmine rice under cold water until the water runs clear to remove surface starch—this keeps cooked rice fluffy and prevents clumping. Combine the rinsed rice with 1 1/2 cups water in a small saucepan, bring to a boil, then reduce to a low simmer, cover and cook 12–15 minutes until water is absorbed. Remove from heat and let rest, covered, for 10 minutes so the steam finishes cooking the grains; fluff with a fork just before serving.

Prepare the steak for quick, even cooking: Pat the 10 oz flank steak dry and season lightly with 1/2 tsp kosher salt and 1/4 tsp black pepper. Toss the slices with 1 tsp cornstarch—this thin coating helps the meat brown quickly, sears to a glossy edge, and slightly thickens any pan sauce for a silky finish.

Prep aromatics and vegetables: Mince 2 cloves garlic and grate a 1-inch piece of ginger. Trim and, if needed, slice the mixed vegetables so pieces are uniform (about 1/4–1/2" thick). Uniform size ensures everything cooks at the same rate and produces consistent texture.

Heat the pan and sear the beef: Place a large heavy-bottomed skillet or a wok over high heat and let it get very hot—this enables maillard browning which builds deep savory flavor. Add 1 tbsp neutral oil and swirl. Working in a single layer (do not overcrowd), add the steak slices and sear 60–90 seconds per side until nicely browned but still medium-rare to medium; this quick sear keeps flank steak tender. Remove the beef to a plate and tent loosely with foil to rest; resting lets juices redistribute.

Stir-fry the vegetables: Keep the pan over high heat, add another small splash of oil if needed, then add the prepared mixed vegetables. Stir-fry for 2–3 minutes until bright, crisp-tender—you want them cooked through but still with snap and color. The high heat cooks quickly so vegetables retain texture and nutrients.

Add aromatics to bloom flavor: Push vegetables to the side, add the minced garlic and grated ginger to the hot pan for 20–30 seconds. Cooking these briefly releases their aromatic oils without burning them; garlic burns quickly and becomes bitter, so keep it moving.

Bring everything together: Return the seared beef and any accumulated juices to the pan. Add 2 tbsp low-sodium soy sauce and toss to coat—soy supplies saltiness and umami while the cornstarch on the beef helps create a glossy coating. Stir-fry everything together 1–2 minutes just to heat through and marry flavors.

Finish with sesame oil and rest: Remove the pan from direct heat and drizzle 1 tbsp sesame oil (optional) to add a toasty, nutty aroma—sesame oil has low smoke point and is best used as a finishing oil. Taste and adjust seasoning with a pinch of salt or extra soy sauce if needed.

Plate and garnish: Divide the cooked jasmine rice between two plates. Spoon the beef and vegetable stir-fry over the rice. Garnish with sliced scallion and a sprinkle of toasted sesame seeds for contrast in color and a subtle crunch.

Serve promptly: Stir-fries are best eaten immediately while the beef is hot and vegetables retain their crispness. Leftovers keep but the texture will soften after reheating.