FIRST STEP: ROAST THE CHICKEN

1. Preheat the Oven: Begin by preheating your oven to 400°F (200°C). This temperature will ensure that the chicken gets perfectly roasted, juicy, and tender.
2. Season the Chicken: In a small bowl, combine the olive oil, garlic powder, smoked paprika, dried thyme, salt, and pepper. Rub this seasoning mixture over both sides of the chicken breasts. Squeeze the lemon juice over the chicken to add brightness and enhance the flavors.
3. Roast the Chicken: Place the seasoned chicken breasts on a baking sheet lined with parchment paper. Roast for 25-30 minutes, or until the chicken reaches an internal temperature of 165°F (74°C). Once cooked, remove from the oven and let the chicken rest for 5-10 minutes. Slice the chicken into thin strips or bite-sized pieces, ready to assemble the sandwich.

SECOND STEP: MAKE THE RED ONION JAM

1. Sauté the Onions: While the chicken is roasting, heat olive oil in a medium skillet over medium heat. Add the thinly sliced red onions and sauté for about 10-12 minutes, stirring occasionally, until the onions become soft and golden brown.
2. Add the Sweeteners: Add the balsamic vinegar and honey to the onions. Stir well to combine. Continue cooking the mixture for another 5-7 minutes, allowing the vinegar to reduce and the jam to thicken. Season with salt and pepper to taste.
3. Cool: Once the red onion jam has reached a thick, syrupy consistency, remove from heat and let it cool to room temperature. This jam will add a rich, sweet contrast to the savory elements of the sandwich.

THIRD STEP: PREPARE THE HERB AIOLI

1. Combine the Ingredients: In a small bowl, whisk together mayonnaise (or Greek yogurt), olive oil, lemon juice, Dijon mustard, and a pinch of salt and pepper.
2. Add Fresh Herbs: Stir in the freshly chopped parsley and basil to give the aioli a bright, herbaceous flavor. If you prefer a smoother consistency, you can blend the mixture with a hand blender or food processor.
3. Taste and Adjust: Taste the aioli and adjust the seasoning if needed. You can add a little more lemon juice for tanginess or more mustard for a sharp flavor.

FOURTH STEP: ASSEMBLE THE SANDWICH

1. Prepare the Focaccia Bread: Slice the focaccia bread into even pieces. If desired, you can lightly toast the slices in the oven or on a grill pan for extra crunch and flavor. Drizzle a little olive oil on the bread for added richness.
2. Spread the Herb Aioli: Spread a generous layer of the herb aioli on the bottom half of each focaccia slice. The creamy, tangy aioli will act as the perfect base for all the other ingredients.
3. Layer the Chicken: Place a few slices of roasted chicken on top of the aioli. The warm chicken will pair beautifully with the aioli and the other components.
4. Add the Red Onion Jam: Spoon a portion of the red onion jam over the chicken. The sweet, caramelized onions will complement the savory chicken and the richness of the goat cheese.
5. Add Goat Cheese and Greens: Crumble the goat cheese over the chicken and onion jam. Top with a handful of fresh arugula or spinach if desired. The greens will add a nice peppery bite and freshness to balance the richness.
6. Finish and Serve: Place the top piece of focaccia bread on the sandwich and press gently to compact everything. Slice the sandwich in half and serve immediately, or wrap it up for a take-along lunch.