Make the sauce:

1. Add all ingredients (except water) to a mixing bowl and mix until combined.
2. Slowly add water, 1 tbsp at a time, and whisk until creamy and smooth.
3. Taste and adjust to your preference.

Prep the ingredients:

1. Finely julienne cucumber, carrot and lettuce, set aside.
2. Soften vermicelli noodles by soaking in a big bowl of hot water or prepare according to instructions on packet.
3. Slice prawns in half lengthwise and devein.

Make the rolls:

1. Fill a plate or a shallow bowl with warm water. Take a sheet of rice paper and submerge it in the water for 2-3 seconds to soften it.
2. Place on rice paper coriander (cilantro) / mint (if using), 3 prawns, lettuce, carrot, cucumber, and vermicelli noodles.
3. Fold the left and right sides of rice paper in, then roll firmly from the bottom upwards and seal the roll.
4. Repeat with remaining sheets of rice paper.