Start by heating olive oil in a large pan over medium-low heat. Add minced garlic and stir until it’s fragrant and golden. Toss in the spinach and cook until wilted. Be sure to drain excess moisture and chop it once cooled.
Using the same pan, sauté the diced mushrooms in olive oil. Season with salt and pepper, and cook until they release their liquid and become tender. Allow them to cool before mixing.
Combine the cooled spinach, mushrooms, shredded fontina, and a portion of the breadcrumbs in a bowl. Mix everything thoroughly to create a unified filling.
Pound the chicken cutlets to an even thickness of about ¼ inch. Season both sides with salt and pepper. Spoon 2-3 tablespoons of filling onto each piece, roll them tightly, and secure with toothpicks. Gently dredge each roll in flour.
Preheat olive oil in a large pan and sear the chicken rolls on all sides until golden brown. Don’t overcrowd the pan; work in batches if necessary.
Reduce the heat and sauté sliced garlic in the pan. Pour in the white wine and chicken stock, scraping up any browned bits for extra flavor. Add lemon juice and simmer until the liquid is reduced.
Place the chicken rolls into the sauce, sprinkle with breadcrumbs, and add the butter. Bake in a 375°F oven for 15-20 minutes or until the chicken reaches 160°F internally.
Once baked, sprinkle the rolls with fresh parsley. Allow them to rest for about 5 minutes before serving.