1. Grate the kashkaval into a bowl and set aside. Cut the tomatoes into thin slices.
2. Coat one side of the slices of toast with soft butter and the other side with pesto.
3. Sprinkle the pesto side of one slice generously with grated kashkaval, put 2 tomato slices on top, add 5-6 leaves of fresh basil, season with salt and pepper and, finally, add a little more kashkaval.
4. Place the second toast side on top (butter side up), place on a grill pan and press with a spatula. Grill on medium heat until golden brown and the cheese melts.