1. Rinse the dry beans several times; cook in salted water on simmer until tender (about 2-1/2 hours). Drain and reserve.
2. Drop the prawns into a saucepan of boiling salted water. Cook 3 minutes.
3. Shell the prawns as soon as they have cooled enough to touch.
4. Combine the prawns with the drained beans, tomatoes and basil. Toss with olive oil and season lightly with salt and pepper. Serve warm.

You can use a can of beans and eliminate the first step. Add crushed garlic if desired.