In a large saucepan, cook the pasta according to the package instructions until al dente. Drain, do not rinse, and set aside.
In another large saucepan, heat the heavy cream, hot pepper sauce, garlic, black pepper and cayenne, if using, over medium heat, stirring until well blended. Season to taste with salt. Add hot pasta and chicken and stir until well coated and warmed through.
Remove the pasta from the heat and stir in blue cheese and scallions. Serve immediately.