Bring a large pot of water to a boil.
In a large, deep skillet, heat the EVOO over medium-high. Stir in the fennel seed. Add the chicken and cook until browned and crumbly, about 5 minutes. Add the chopped fennel, celery, onion and garlic; season with salt and pepper. Partially cover the pan and cook over medium heat until the vegetables soften, 8 to 10 minutes. Add the wine, scraping the bottom of the pan. Add the stock and half-and-half. Reduce the heat to medium-low and simmer the ragu while the pasta cooks.
Salt the boiling water, then cook the pasta until al dente. Drain, reserving half a mug of cooking water. Stir the cooking water into the ragu, then toss the pasta with the ragu and 1/2 cup of the cheese; season. Garnish with the chopped fennel fronds and celery leaves. Serve with more cheese.
