Cheesy Chicken Baguette

Ingredients

• 3 tablespoons butter
• 1 medium onion, thinly sliced
• 1 cup sliced mushrooms, caps only
• 2 boneless skinless chicken breast halves (pounded thin)
• 1/4 teaspoon dried thyme leaves, crushed (optional)
• salt & fresh ground pepper, to taste
• crushed red pepper flakes, to taste (optional)
• garlic powder
• mayonnaise, for serving (optional)
• mustard, for serving (optional)
• 1 French baguette, halved lengthwise (about 12-inch long)
• 3/4 cup jarlsberg cheese or 3/4 cup swiss cheese, shredded
• 2 slices bacon, crisp-cooked and crumbled