Melt 2 tablespoons butter in a saucepan over low heat. Cook and stir shallots in hot butter until translucent, about 5 minutes. Add parsley and saute for 5 minutes; season with pepper and salt.
Carefully pour cognac over shallot mixture; cook and stir until flames have disappeared, 2 to 3 minutes. Add beef stock and bring to a boil; reduce heat, add creme fraiche, and simmer until sauce is slightly reduced, about 5 minutes. Stir 2 tablespoons butter into sauce until melted.
