In a small bowl, blend together the butter, Parmesan cheese, salt and pepper. Spread some of the butter mixture on one side of each slice of bread. In a nonstick skillet over medium-high heat, cook the bread slices, butter side down, for about 3 minutes till crisp and deep brown. Set aside to cool.
For each sandwich, spread one slice of toast with honey mustard and layer with avocado, tomatoes, onions and bell pepper. Place another slice of toast on top.