In a skillet, heat add olive oil and butter. Add thinly sliced onions, a pinch of salt and pepper, and cook for about 12-15 minutes until the onions are soft and a little caramelized

Add the chicken breasts to the slow cooker, followed by the cooked onions, minced garlic, chicken broth, and kosher salt & black pepper.

In a small bowl, whisk flour and Worcestershire sauce together. Whisk the mixture into the broth on top of the chicken. Cover and cook on low for 7-8 hours.

Remove the chicken, place onto a cutting board, and cut into pieces or lightly shred.

Preheat oven to 415 degrees. On a sheet pan, lay the rolls open. Top each roll with about 4 ounces of chicken. two tbsp of mozzarella. Then close the rolls.

Bake ar 415 degrees for about 6-10 minutes or until the bread is crispy and the cheese is nicely melted. Serve each with some au jus for dipping. Serves 6.