Start by preheating your panini press if you’re using one. Take your slices of brioche bread and lightly butter one side of each. This buttered side will face out during grilling for a golden, crispy finish. Slice your mozzarella and tomatoes ahead of time so the sandwich comes together quickly.
Place four slices of bread butter-side down. On each, layer sliced chicken evenly, followed by mozzarella cheese, tomato slices, and a few fresh basil leaves. Drizzle a little balsamic glaze over the top for a tangy burst of flavor. Cover each sandwich with the remaining bread slices, butter-side up.
Place the sandwiches on your preheated panini press or into a hot skillet. If using a press, close the lid and grill for 1–2 minutes until the bread is golden brown and the cheese begins to melt. If using a skillet, press the sandwich down slightly with a spatula, grill each side for about 2 minutes, then carefully flip and repeat.
Once grilled, remove the paninis and let them sit for a minute. Slice them in halves or quarters, depending on your serving preference. Serve warm with a light salad or chips on the side. The crispy crust, melty cheese, and flavorful filling make each bite incredibly satisfying.