Wash and dry all produce. Place rice and 11/2 cups water in a small pot. Cover and bring to a boil, then reduce heat to low. Simmer until tender and water is absorbed, about 15 minutes. Keep covered off heat until meal is ready. Meanwhile, trim and thinly slice scallions, separating greens and whites.

Place 5 tsp vinegar (1 bottle; save rest for beef), 1 tsp sugar, and a few pinches of salt in a medium bowl. Trim cucumber ends. Using a peeler, shave cucumbers lengthwise into ribbons, rotating until you get to the seedy core; discard core. Add ribbons to bowl with vinegar and toss to coat. Set aside.

Heat a drizzle of oil in a large pan over medium-high heat (use nonstick if you have it). Add carrots and cook, tossing, until tender but still a little crisp, about 1 minute. Season with salt and pepper. Transfer to a plate and set aside.

Heat a large drizzle of oil in same pan over medium-high heat. Add scallion whites and cook until fragrant, about 30 seconds. Add beef and a pinch of salt and pepper, breaking up meat into pieces. Cook until browned, 5-7 minutes. Stir in 1 TBSP sesame seeds (1 pack). Pour in remaining vinegar. Cook 30 seconds, then stir in bulgogi sauce and bring to a simmer. Remove pan from heat. Season with salt and pepper.

While beef cooks, stir together sour cream and sriracha (to taste) in a small bowl. Stir in water 1 tsp at a time until mixture has a drizzling consistency. Season with salt.

Fluff rice with a fork and stir in 2 TBSP butter. Season with salt and pepper. Divide rice between bowls. Arrange beef, carrots, and cucumbers on top, next to each other. (TIP: Drain any excess liquid from the cucumbers before adding.) Drizzle crema over everything. Garnish with scallion greens and remaining sesame seeds.