To make the salad rolls: Pour boiling water into a deep baking dish and stir in salt to dissolve. Add vermicelli noodles and soak 2 minutes, until soft. Remove noodles from water (leaving the water in the dish), and transfer to a bowl. Sprinkle fish sauce and lime juice over top, and stir.

Soak a clean dishtowel in warm water, then ring it out and lay on work surface. Take one rice wrapper and dip it in the reserved hot water for about 15 seconds, just until softened. Lay it on the damp towel, and top the bottom third with some noodles, carrot, cucumber and bean sprouts.

Fold the bottom of the wrapper up over the filling, tuck in the sides, and roll the whole thing up. Transfer to a plate and cover with damp paper towels. Repeat with remaining rice wrappers.

To make peanut sauce: Microwave peanut butter for 30 seconds to loosen. Stir in remaining ingredients and add hot water as needed to reach desired consistency.