Wash and dry all produce. In a small pot, combine rice, 3/4 cup water (11/2 cups for 4 servings), and a pinch of salt. Bring to a boil, then cover and reduce to a low simmer. Cook until rice is tender, 15-18 minutes. Keep covered off heat until ready to serve. Meanwhile, trim and thinly slice scallions, separating whites from greens.

In a medium bowl, combine half the vinegar (you’ll use the rest later), 1/2 tsp sugar (1 tsp for 4 servings), and a pinch of salt. Trim ends from cucumber. Using a peeler, shave cucumber lengthwise into ribbons, rotating as you go, until you get to the seedy core; discard core. Toss ribbons in bowl with vinegar mixture. Set aside, tossing occasionally, until ready to serve.

Heat a drizzle of oil in a large, preferably nonstick, pan over mediumhigh heat. Add carrots and cook, stirring, until just tender, 1 minute. Season with salt and pepper. Turn off heat; transfer to a plate.

Heat another drizzle of oil in same pan over medium-high heat. Add scallion whites and cook until fragrant, 1 minute. Add beef and a pinch of salt and pepper. Cook, breaking up meat into pieces, until browned and cooked through, 4-6 minutes. Stir in half the sesame seeds (you’ll use more later) and remaining vinegar. Cook for 30 seconds, then stir in bulgogi sauce. Bring to a simmer, then immediately turn off heat. Season again with salt and pepper.

Meanwhile, in a small bowl, combine sour cream and sriracha to taste. Stir in water 1 tsp at a time until mixture reaches a drizzling consistency. Season with salt.

Fluff rice with a fork. Stir in 1 TBSP butter (2 TBSP for 4 servings) and season with salt and pepper; divide between bowls. Arrange beef, carrots, and pickled cucumber on top. (TIP: Drain any excess liquid from cucumber before adding.) Drizzle crema over everything. Garnish with scallion greens and as many remaining sesame seeds as you like.