steps

1. 1.

   In a skillet over medium heat, add olive oil and sliced onions. Sauté until caramelized, stirring occasionally. Set aside.

2. 2.

   Season the chicken breasts with salt and pepper on both sides. Grill or cook in a skillet until thoroughly cooked.

3. 3.

   Toast the bread slices until lightly golden.

4. 4.

   Place a slice of Swiss cheese on top of each chicken breast, allowing it to melt slightly.

5. 5.

   Assemble the sandwich by placing the cheesy chicken breast on one slice of bread. Top with caramelized onions and cover with the second slice of bread.

6. 6.

   Cut the sandwich in half if desired and serve hot.