Bring water to a boil for pasta.
Slice shallots and garlic thinly; chop parsley coarsely (½ cup). Grate cheese (about ½ cup).
Preheat large sauté pan on medium-high 2–3 minutes.
Season chicken with ½ teaspoon each salt and pepper.
Place oil and chicken in pan; cook 4–5 minutes on each side until browned and 165°F.
Remove chicken from pan.
Add mushrooms and remaining ½ teaspoon each salt and pepper to same pan.
Cook 7–8 minutes, stirring occasionally, until mushrooms soften.
Stir in Calabrian peppers, shallots, and garlic.
Cook 2–3 minutes, stirring occasionally, until shallots soften.
Meanwhile, cook pasta following package instructions.
Drain, reserving ½ cup pasta cooking water.
Stir wine into mushroom mixture and bring to a simmer; cook 3 minutes or until reduced by three-fourths.
Stir in heavy cream and bring to a simmer; cook 3 minutes or until reduced by one-half.
Slice chicken; return chicken and any accumulated juices to pan.
Reduce heat to low.
Add pasta, butter, pasta cooking water, and ¼ cup cheese to pan.
Cook 1–2 minutes, stirring continuously, until pasta is evenly coated.
Top with parsley and remaining ¼ cup cheese.
Serve.
