Place half of the mango and half of the pawpaw into the container of a food processor or blender along with balsamic vinegar. Puree until smooth and set aside.
Melt butter in a small frypan over medium heat. Add almonds and cook stirring constantly until lightly browned. Add brown sugar and stir to coat. Remove from heat, and pour candied almonds onto a piece of waxed paper, separating any clumps. Set aside to cool.
Just before serving, place cos lettuce in a large serving bowl. Cube remaining mango and papaya halves, and toss gently with avocado and lettuce. Drizzle the pureed fruit over the salad and lightly salt. Sprinkle with candied almonds and serve immediately.