Start by seasoning the chicken breasts with salt, pepper, and dried thyme. Heat 1 tablespoon of olive oil in a large skillet over medium heat. Once hot, add the chicken breasts and cook for about 6-7 minutes on each side or until the internal temperature reaches 165°F. Remove from the skillet and let them rest for a few minutes before slicing.
In the same skillet, add the remaining 1/2 tablespoon of olive oil. Add the sliced red onions and sprinkle with granulated sugar. Sauté for about 5-7 minutes, stirring occasionally, until the onions are caramelized and golden brown. Add the minced garlic and crushed red pepper flakes, cooking for an additional minute until fragrant. Stir in the balsamic vinegar and cook for another minute to combine. Remove from heat.
In a mixing bowl, combine the thawed spinach with mayonnaise. Mix well until smooth and creamy. This will serve as a delicious spread on the panini.
Preheat your panini press or grill pan. Roll out the refrigerated pizza crust on a lightly floured surface to your desired thickness. Cut the dough into rectangular pieces that will fit your press or pan. Spread a generous layer of the spinach mixture on one side of each rectangle. Layer the sliced chicken on top, followed by the caramelized onions and provolone cheese. Top with another piece of dough, spinach side down.
Place the assembled panini in the press or grill pan. If using a grill pan, you may need to use a heavy skillet on top to press down the sandwich. Cook for about 4-5 minutes, or until the crust is golden brown and the cheese has melted. Carefully flip halfway through if using a grill pan.
Once the panini is done, remove it from the heat and let it cool for a minute. Cut it in half and serve warm. Enjoy your Chicken Florentine Panini with a side of your favorite salad or chips for a complete meal!
