Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Add fennel sausage, breaking it into pieces and allow it to brown for about 3 minutes. Stir and cook for additional 4–5 minutes until browned and cooked through.

Lower heat to medium and add finely diced onion and fennel bulb. Sauté for about 8 minutes until soft and translucent. Add minced garlic and a pinch of red pepper flakes, stirring for about 45 seconds.

Pour in 1 cup of dry white wine, scraping the bottom of the pan. Allow to simmer and reduce by half, about 3–4 minutes. Return sausage, then add 2 cups chicken broth and 1 bay leaf. Cover slightly ajar and simmer for 20 minutes.

Remove bay leaf and stir in 1 cup of heavy cream. Simmer uncovered for 5 minutes, adjusting seasoning with salt and pepper to taste.

In a large pot, boil salted water and add fresh pappardelle. Cook for 2–3 minutes until tender. Reserve 1 cup pasta water before draining.

Transfer drained pappardelle to skillet with creamy ragu. Toss over medium-low heat, adding reserved pasta water to achieve desired consistency. Stir in 2 tablespoons of cold butter and half of the Parmigiano-Reggiano.

Squeeze in fresh lemon juice if desired. Serve immediately topped with remaining Parmigiano-Reggiano, fennel fronds, and black pepper.