In a medium pan (preferably cast-iron), heat the oil over high heat. Add the beef, and press it into a single layer with a spatula. Cook until the bottom is crispy and browned (not burnt!), about 5 minutes. Break it up with your spatula and cook through. Drain any fat.
Add the scallions and jalapeno to the pan, and cook until the jalapeno is softened. Stir in the ginger and garlic and cook until fragrant. Lastly, add the soy sauce, fish sauce, lime juice, hot sauce, and brown sugar to the pan. Stir to combine. Season with salt and pepper. Taste, and add more seasonings as necessary.
Serve the beef in lettuce cups with pickled vegetables and rice. (Alternatively, you can serve it over bowls of rice). Add additional herbs, lime wedges, and hot sauce to taste.