Preheat grill or broiler. Bring 3 cups water to boil in a small saucepan
, and set up an ice bath nearby.
In a mixing bowl, stir together the cooked beans, rosemary, 2 tablespoons of the olive oil, red onion
, and the juice and zest
of lemon. Season the mixture with salt and pepper.
Plunge the mint leaves into the boiling water for 30 seconds and remove to ice bath. When the mint leaves have cooled, remove them from the bath, and gently squeeze to remove any excess liquid. Place the mint and parsley leaves in a food processor
and process for 1 minute with 3/4 cup extra-virgin olive oil. Season with salt and pepper. Set aside.
On a large plate, arrange the beans in 1 pile and the mache
drizzled with oil in another pile.
Season the prawns with salt and pepper, brush with oil, and grill
until opaque and cooked through, about 7 minutes.
Remove the prawns
from the grill and stack them in another pile on the plate.
the dish with the mint oil and serve immediately.