Preheat your oven to 375°F (190°C). Season the chicken breasts with salt, pepper, and your favorite herbs. Place them on a lined baking sheet and roast for 25–30 minutes, or until they reach an internal temperature of 165°F (74°C) and are beautifully golden. Let the chicken cool slightly before slicing it into juicy pieces for your sandwich.

In a medium saucepan, combine sliced red onions, a few tablespoons of sugar, and a splash of vinegar. Cook over medium-low heat for 20–25 minutes, stirring occasionally, until the onions caramelize and develop a rich, deep color. Once thickened and sweetened, let the jam cool before layering it onto your sandwich.

In a bowl, mix together mayonnaise, finely minced fresh herbs (like parsley and basil), a clove of minced garlic, and a squeeze of lemon juice. Stir well until all ingredients are well incorporated. Let the herb aioli sit for at least 30 minutes to allow the flavors to meld, which will enhance its taste in your Roasted Chicken Focaccia Sandwich.

Slice your focaccia bread horizontally, creating a thick sandwich base. Begin layering with the sliced roasted chicken atop the bottom half, followed by generous dollops of creamy goat cheese. Top with the sweet red onion jam and a spread of herb aioli, ensuring each bite is packed with flavor.

Cut the assembled sandwich in half for easy handling and a delightful presentation. Serve immediately alongside a fresh side salad or crispy potato chips for a satisfying meal.