In a food processor or blender, combine basil leaves, garlic, pine nuts, and Parmesan cheese. Season with Kosher salt and black pepper. Blend until finely chopped.

With the motor running, slowly drizzle in olive oil until the pesto is smooth and creamy. Transfer to a bowl and set aside.

In a mixing bowl, combine shredded chicken and basil pesto with Greek yogurt. Stir until evenly coated.

Preheat the oven to 350°F (175°C). Slice the baguette and toast for 5-7 minutes until golden brown.

Layer the bottom half of each baguette with arugula, tomato slices, and mozzarella cheese.

Scoop the chicken pesto mixture onto each sandwich, ensuring even distribution.

Place the top half of the baguette over the filling, cut in half if desired, and serve immediately.