For the croutons, heat the olive oil and butter together in a non-stick frying pan, add the torn bread and fry gently until golden and crisp.
For the salad, place the chopped lettuce and tomatoes into a large bowl. Stir in the crunchy croutons.
In a small bowl, whisk together the olive oil and balsamic vinegar and drizzle it over the salad. Mix to combine. Scatter the basil over the salad.
Heat a non-stick frying pan, add the prosciutto and fry for 1-2 minutes, or until crisp.
To serve, pile the salad onto a serving plate and top with the prosciutto.