Grill slices of bread on both sides until golden brown.
Wash the zucchini and cut into large slices. Place the zucchini in a separate saucepan, add the broth and cook for 15 minutes. Then add the basil leaves, butter, and grated Parmesan cheese. Remove the pan from the heat.
Grind the soup into a smooth paste using a blender. Season with pepper and salt, if necessary.
Place a slice of bread in a separate bowl and top with hot soup. Serve on the table.