Rinse the lentils under cold running water to remove any grit then tip into a saucepan and add enough cold water to cover them by a good 3-4cm. Add the bayleaves and shallot and bring up to the boil. Simmer steadily for around 20 minutes until they are tender but not falling apart. Drain and remove the bayleaves and shallots. Whilst the lentils are cooking make the dressing in a large roomy bowl. Whisk together the oil, balsamic vinegar and garlic. Taste as you go, adding more vinegar as necessary - there should be a good balance of sweet and sharp. Stir through the tomatoes, shallots and basil and season with a little salt and freshly ground black pepper. Add the warm lentils to the dressing and mix well. Add the washed spinach leaves to a large saucepan. Cover with a tight fitting lid and cook over a medium heat for around 5 minutes by which time they should have wilted down. Drain and squeeze out any excess water then stir through the lentils. Cover with foil to keep warm and set aside for the flavours to infuse whilst you cook the fish. Spread out the proscuitto slices on a chopping board and top each with a piece of fish. Season with a little salt and freshly ground black pepper and a couple of basil leaves. Drizzle over a little olive oil and wrap the ham around, covering the fish as much as possible. Lay the fish in a roasting tin and drizzle over a little more olive oil. Bake in the oven at 180°C for around 15 minutes or until the fish is opaque and cooked through. The cooking time may vary a little depending on the thickness of your fish. Serve the fish on top of the lentils, drizzled with the roasting juices.