Cook bacon until crisp and set aside on a paper towel to soak up the grease, if necessary.
You can toast or leave untoasted the bread. Cut bread into sandwich slices.
Spread a little bit of mayonnaise or pesto onto one side of each slice of bread.
Layer the bacon, the salad greens, the tomatoes, the red onion, and basil leaves, the avocado and alfalfa sprouts if using onto one slice of bread. I use about four basil leaves for each sandwich. Season sandwich with salt and pepper if desired.
Place the other slice of bread on top and very gently push down on the sandwich.