Place a large pot of water on to boil for pasta. When it comes to a boil, salt it and add the pasta to cook to al dente. Strain pasta reserving 1 cup cooking liquid.
While the water is coming to a boil, in a large mixing bowl combine the chicken, salt and pepper, rosemary, fennel seeds, garlic, crushed red pepper flakes, ricotta cheese, 1/2 cup grated Parmigiano - a rounded handful, egg and bread crumbs. *If the mixture seems too wet, add a handful of bread crumbs and mix together.
Form 8 large round balls, about 3 to 4-inches. Coat balls in a couple of tablespoons of extra-virgin olive oil and lightly grease a baking sheet with 1 tablespoon extra-virgin olive oil. Arrange balls on the baking sheet and roast 17 to 18 minutes until juices run clear.
Defrost spinach in microwave 8 to 10 minutes on "defrost" setting depending on the microwave. Place the boxes in a shallow dish to catch any run off.
While the meatballs roast, in a medium sauce pot over medium heat, melt butter, whisk in flour, cook 1 minute then whisk in stock and milk, season with salt, pepper and nutmeg and thicken 5 to 6 minutes. Stir in the remaining 1 cup grated Parmigiano and reduce heat on lowest setting.
Wring spinach completely dry in clean kitchen towel then separate as you add it to the sauce. Also add the reserved 1 cup pasta cooking liquid.
Toss pasta with the spinach-white sauce and adjust seasonings.
Serve Florentine Mac-n-Cheese with 2 meatballs per person along side.