2 tablespoons unsalted butter
1 clove garlic, minced
1/2 red bell pepper, thinly sliced
1 rib celery, thinly sliced
1 pound cultivated mussels,(greenshell clams) scrubbed
6 ounces linguine pasta
3 tablespoons heavy cream
3/4 teaspoon salt
1/4 teaspoon black pepper
3 tablespoons chopped fresh flat-leaf parsley
Cook shallots in butter in a 12-inch heavy skillet over moderate heat, stirring, until shallots are softened, about 5 minutes.
Stir garlic, bell pepper, and celery and cook, stirring occasionally, until pepper and celery are just tender, about 4 minutes.
Add mussels and cook over moderately high heat, covered, until they just open, 4 to 6 minutes, checking periodically after 4 minutes and transferring mussels as opened to a bowl. (Discard any unopened mussels after 6 minutes.)
While sauce is cooking, cook linguine in a 6-quart pot of boiling salted water until al dente. Reserve 3/4 cup cooking water and drain linguine in a colander.
Add linguine to skillet along with cream, salt, pepper, and 1/3 cup pasta cooking water and bring to a simmer. Add mussels and toss carefully, adding more cooking water if pasta seems dry. Serve immediately, sprinkled with parsley.