Heat a panini press or skillet over medium high heat. Lightly spray with pan spray to avoid sticking.
Slice focaccia bread in half to make a top and bottom for the sandwiches.
Spread pesto on bottom slice of focaccia. Layer chicken, cheeses and tomatoes over pesto. Place top half of focaccia over filling. Cook in panini press for 3-5 minutes until outside is toasted and cheese is melted.
If using a skillet, press sandwich down onto hot skillet using a sauce pan. Flip and cook the other side. Cook until bread is toasted and cheese is melted.
Slice into two equal portions and serve hot.
To make your own cooked chicken place uncooked chicken breasts in a medium saucepan. Cover with water or chicken broth. Bring to a boil, cover and reduce heat to low. Simmer for 10 minutes. Drain and slice.