In a small bowl, stir together the mayonnaise, chipotle, adobo sauce, salt, and pepper.
Place the shredded chicken in a medium heatproof bowl. Cover and microwave in 15-second increments, stirring between each, until warmed through (about 1 minute). Ensure the chicken reaches an internal temperature of 165°F (74°C).
Place the bottom halves of the focaccia on a clean surface. Spread the chipotle mayo on each slice, then layer with fresh basil. Add the warmed chicken on top, seasoning with pepper. Layer mozzarella and tomato over the chicken, and generously season with salt and pepper. Top with thinly sliced red onion. Spread the remaining chipotle mayo on the top halves of the focaccia, then close the sandwiches.
Heat a panini press or a large heavy pan over medium heat. Brush with olive oil. Working in batches if necessary, add the sandwiches to the panini press or pan; close the press or top the sandwich with another heavy pan. Cook the sandwiches until the focaccia is crisp and golden brown on both sides and the mozzarella is melted, about 3–4 minutes. If toasting in a pan, cook until golden brown on the bottom (about 2–3 minutes), then remove the top pan, flip the sandwiches, and continue to cook until golden brown on top and mozzarella is melted, about 1–2 minutes more.
Mix all of the ingredients for the lemonade and serve over ice if desired.
Serve the frontega chicken panini with carrots and hummus, pickle spears, and homemade lemonade.