Drain soaked beans, place in 4 litre saucepan with 8 cups water and bring to a boil. Lower heat to high simmer and cook until tender, yet slightly firm to the bite. Drain and cool. Place cool beans in a mixing bowl and add onion, mint and extra virgin olive oil. Season with salt and pepper, toss to coat and set aside.
Place remaining half cup of oil into a blender and add chilis, pepper flakes and capers and blend until smooth. Remove to bottle with lid and set aside.
Preheat grill.
Clean and gut anchovies and place on hottest part of grill, and cook through, about 1 minute per side. Meanwhile, add vinegar to bean mixture and toss to mix. Add Frisee and stir to coat. Place on platter. Remove fish from grill, arrange around salad and serve.