Heat 2 inches oil in a 4-quart heavy pot over moderate heat until a deep-fat thermometer registers 365 degrees.
While the oil is heating, make dipping sauce by stirring together soy sauce, lime juice, and sugar until sugar is dissolved. Set aside. Whisk together flour and sesame seeds and whisk in beer until batter is smooth.
Toss about 10 beans in batter until coated. Add to oil 1 at a time (to keep separate) and fry, turning, until golden, about 1 1/2 minutes. Transfer with tongs to paper towels to drain and sprinkle with salt to taste. Coat and fry remaining beans in same manner.
Serve beans with dipping sauce.
Recipe courtesy of Gourmet Magazine