Bring a large pot of water to a boil with 1 Tbsp salt. Cook pasta in boiling water until it is al dente. Drain and hold.
In a skillet over medium high heat, melt the butter until it froths. Add the scallions, garlic, shallots, and seafood. Sauté until aromatic and the shrimp are pink, about 3 minutes. The seafood will be slightly undercooked at this point.
Add wine, stirring from the bottom of the skillet. Reduce wine to half, about 6 minutes.
Push seafood to the side of the skillet, add 2 Tbsp of butter and swirl gently. Slowly add cream, whisking gently so that the cream thickens.
Add tarragon, marjoram, salt and pepper, and Tabasco sauce. Stir seafood and sauce together to combine.
Plate the fettuccine, pour the sauce over, and garnish with the parsley.