If possible, make and wrap the rolls the evening before so the flavors can meld and the beef rolls can firm up in the fridge. It makes skewering and grilling a little easier.
In a large bowl, combine the ground beef with green onion, mint, Thai Chiles, sugar, fish sauce, salt, and pepper. Mix thoroughly, but lightly, with fingertips.
Using a 1 tablespoon scoop, portion into 18 small mounds. Form into a log shape, about 1 1/2 inches long, pressing enough so the meat mixture holds together.
Wrap each log with a large basil leaf, or if basil leaves are smaller wrap with two, overlapping the long way. Thread onto skewers. (See note.)
To grill, prepare charcoal or heat gas or indoor grill to medium-high. When heated, turn down to medium, brush the grill and the rolls with a little oil, and add the skewers, at a right angle to the grates.
Brush the top of the rolls with oil before turning and placing on a fresh area of the grill.
Grill for a total of six to eight minutes over medium heat, until the desired doneness. The rolls will be very soft at first but will firm up as cooked. If necessary, use a thin spatula to help loosen the rolls for turning and removing.
Serve with the Sweet Chili Sauce.
Note on wrapping and threading the skewers: