Bring a large pot of salted water to a boil. Add the fettuccine and cook 8–10 minutes until al dente, stirring occasionally; drain and set aside.
Meanwhile, melt 2 tablespoons unsalted butter in a large saucepan over medium-high heat. Season the chicken pieces with 1/2 teaspoon salt and 1/2 teaspoon pepper, then add to the pan.
Sauté the chicken until golden and cooked through, about 6–8 minutes. Remove the chicken to a plate and set aside.
In the same saucepan, melt the remaining 8 tablespoons butter over medium heat. Add the ricotta, heavy cream, and 2/3 cup grated Parmesan; stir to combine.
Bring the sauce to a gentle boil, then reduce heat to medium-low and simmer about 5 minutes, stirring occasionally, until smooth and slightly thickened. Taste and adjust seasoning with salt and pepper if needed.
Add the cooked chicken and drained fettuccine to the sauce and toss until everything is evenly coated and heated through.
Serve immediately, garnished with extra Parmesan and chopped parsley.