01 - In a large, deep skillet or sauté pan, melt butter over medium heat. Add shallot and garlic; sauté for 1-2 minutes until fragrant but not browned.
02 - Add shrimp to the pan; season with a pinch of salt and pepper. Cook for 2 minutes per side, until just pink. Remove shrimp and set aside.
03 - Pour chicken broth, heavy cream, and milk into the same pan. Bring to a gentle simmer.
04 - Add dry fettuccine, stirring to submerge the pasta. Cook uncovered, stirring frequently, for 10-12 minutes, or until pasta is al dente and liquid is mostly absorbed.
05 - Lower the heat. Stir in Parmesan cheese and red pepper flakes (if using) until melted and sauce is creamy.
06 - Return cooked shrimp and any juices to the pan. Toss to combine and heat through for 1-2 minutes.
07 - Adjust seasoning with additional salt and pepper if needed. Garnish with chopped parsley before serving.