Boil water in a small pot. Remove from heat. Place the noodles in the hot water for 10 minutes to soften, and then drain.
Mix the fish sauce, sugar, and lime juice together. Pour over the noodles and stir in the grated carrots.
Put a stack of the noodle mixture on top of a lettuce leaf. Roll the leaf around the noodles.
Serve with peanut sauce for dipping.