Cut the chicken breasts roughly in half, unwrap and place on top of plastic wrap. Pound the meat to a thickness of about 1.5 centimeters. Drizzle with a tablespoon of oil.
Put the grill pan on high heat, add the chicken breasts. Season with a little salt and pepper and cook for about 3 minutes on each side. Turn them over a few times. When the chicken is almost cooked, add the thick balsamic vinegar and fry for 30 seconds on each side to caramelize. Add a little more balsamic and toss once more. When the chicken is cooked through and caramelized, set the chicken aside.
Heat a large frying pan with high sides. Add finely chopped onion. When the liquid from the onion is gone, add the olive oil, rice and fresh thyme. Mix the rice with oil and onion for about 3 minutes.
Pour in the white wine, let it cook until it is reduced and absorbed into the rice. Add saffron and mix. Start by adding the hot broth. A little at a time. The liquid should come to a boil in the rice between each addition of broth. Repeat until the rice is cooked and almost all the power is used up.
3 minutes before the risotto is fully cooked, add some chopped rosé lettuce.
Turn off the heat. Stir in the butter and grated cheese, stirring until the cheese has melted and the risotto is creamy.
Divide the risotto among 4 plates. Cut the chicken into thin strips and place on top of the rice along with a few sprigs of thyme. Apply a few drops of olive oil.