Place the slices of baguette on a baking pan and toast (I use the broil part of my oven for approximately 2 minutes on each side).
Portion the soup into oven-safe bowls and place on top a baking pan for ease. I then add a nice portion of Mozzarella & Swiss cheese into the mixture before placing my pieces of baguette. I top the baguette with generous amounts of Gruyere cheese. Place the bowls in the oven to bake at 350*F for approximate 20 to 30 minutes to melt the cheese.
If you are like me, you like the crispy melted cheese - to achieve this, broil the soup bowls for an additional 2 to 3 minutes after baking so the cheese is bubbly & browned.