Before starting, wash and dry all produce. Add 1 ¼ cups water and ⅛ tsp salt (dbl both for 4 ppl) to a medium pot. Cover and bring to a boil over high heat. Meanwhile, roughly chop cilantro. Cut cucumbers into ¼-inch rounds. Combine mayo and sriracha in a small bowl. Set aside.
Add rice to the boiling water. Reduce heat to low. Cover and cook until rice is tender and liquid is absorbed, 12-14 min. Remove the pot from heat. Set aside, still covered.
Meanwhile, whisk together vinegar, ¼ cup water and ½ tbsp sugar (dbl both for 4 ppl) in a medium bowl. Add cucumbers and carrots, then toss to coat. Place in the fridge to pickle.
Heat a large non-stick pan over medium-high heat. When hot, add ½ tbsp oil (dbl for 4 ppl), then beef. Cook, breaking up beef into smaller pieces, until no pink remains, 4-5 min.**Carefully drain and discard excess fat.
Add hoisin sauce, soy sauce and half the sesame seeds to the pan. Cook, stirring often, until beef is coated, 1-2 min.
Drain pickled veggies and discard liquid. Fluff rice with a fork, then season with salt, to taste. Divide rice between bowls. Top with beef, pickled veggies and cilantro. Spoon sriracha mayo over top, then sprinkle with remaining sesame seeds.
