Combine the lemongrass, garlic, shallots, chili, fish sauce, lime juice, water, and sesame oil in a bowl.
Wrap the beef tightly in cling film to form a cylinder and chill in the fridge for 30 minutes.
Unwrap the meat and slice it into 5mm thick discs.
Submerge the beef discs in the marinade for 30 minutes.
Thread the beef onto cocktail sticks and coat with sesame seeds.
Griddle the beef for 2 minutes per side until the seeds are toasted.
Stir together the lime juice, fish sauce, water, vinegar, sugar, garlic, chili, and carrot to make the sauce.
Arrange the beef skewers on a plate and serve with the bowl of dipping sauce.