In a large skillet over medium heat, toast peanuts until starting to brown, about 4 minutes. Add onion flakes, if using, and toast until brown, 1–2 minutes. Transfer to a bowl and set aside. Wipe out skillet.

Heat now-empty skillet over medium, add beef and cook, breaking meat apart with back of wooden spoon or spatula, until meat is no longer pink, but not browned, about 5 minutes; season with ½ teaspoon kosher salt.

Meanwhile, add shallots to a fine mesh sieve and rinse under cold water; drain well.

Remove skillet from heat and stir in shallots, scallions, ¼ cup lime juice, fish sauce, serrano(s), lemongrass, and honey. Season with salt to taste and let cool 5 minutes.

Stir in half of the cilantro and half of the mint. Transfer to a serving dish and top with remaining herbs, flaky salt and a handful of reserved toasted peanut and onion flakes. Serve with green cabbage leaves, cooked long-grain rice and remaining toasted peanut mixture.