Prep Your Ingredients & Cook the Pasta: Bring a large pot of water to a rolling boil and salt it generously. Drop in your 1 lb of fettuccine and cook according to package directions until al dente. While the pasta cooks, pat your 1 lb chicken breast dry and season it well with salt and pepper. Now, put on your gloves. Finely mince your 1-3 habanero peppers, remembering to remove the seeds and membrane to control the heat. Mince the 4 cloves of garlic and finely chop the 1 shallot.
Sear the Chicken: In your large, heavy-bottomed skillet, heat 1 tbsp olive oil and 1 tbsp butter over medium-high heat. Once the butter is melted and sizzling, carefully add the seasoned chicken in a single layer. Let it cook without moving for 3-4 minutes, until a deep golden-brown crust forms. Flip the pieces and cook for another 3-4 minutes until cooked through. Work in batches if necessary. Transfer the browned chicken to a clean plate.
Sauté the Shallot: Reduce the heat to medium and add the chopped 1 shallot to the same skillet, stirring to scrape up any delicious browned bits left from the chicken. Cook for about 2 minutes until the shallot softens and turns translucent.
Bloom the Habanero & Aromatics: Add your finely minced habanero peppers. Stir them into the shallots and let them sizzle for about 90 seconds until a sweet, tropical, fruity scent fills your kitchen. Next, add the 4 cloves minced garlic and stir constantly for just 30 seconds until its nutty aroma hits you. Do not let the garlic burn.
Build the Sauce Base: Pour in the 1 cup of chicken broth and the 1 tsp lemon juice. Bring it to a gentle simmer, using your spoon to scrape up any last stubborn browned bits from the bottom of the pan. Let this simmer for about 3-4 minutes, allowing the liquid to reduce slightly.
Make it Creamy: Turn the heat down to low. Slowly pour in the 1 ½ cups of heavy cream, stirring constantly. Let the sauce warm through gently, allowing it to bubble just slightly at the edges. Do not let it come to a rolling boil. Season with a pinch of salt and a few cracks of black pepper.
Bring It All Together: Add the seared chicken and any of its juices back into the simmering cream sauce. Stir to coat. Using tongs, transfer the cooked fettuccine directly from its cooking water into your skillet with the sauce. A little pasta water clinging to the noodles is good.
The Perfect Finish: Turn the heat completely off. Sprinkle in the ¾ cup of freshly grated Parmigiano-Reggiano and the ¼ cup of chopped fresh cilantro. Toss everything together gently but continuously until the cheese melts and the sauce becomes perfectly velvety. Serve immediately in warm bowls.