Place an oven rack in the lower 1/3 of the oven. Preheat the oven to 190°C/gas 5.
Arrange the bread slices in a single layer on a sheet tray. Bake for 10 to 12 minutes until golden. In a small bowl, using a fork, mix the butter and cheese together until smooth.
For the salad:
In a small bowl, whisk together the lemon juice and oil until combined and season with salt and pepper, to taste. Place the lettuce, fennel, basil, and mint in a salad bowl.
Pour the dressing over the salad and toss well.
Spread the Parmesan butter on the toasted bread and serve alongside the salad.