2 teaspoons olive oil
1 tablespoon mustard seeds
2 cloves garlic, minced
1 small onion, minced
2 cups chopped, diced tomatoes
1/4 cup chicken stock
1 teaspoon Dijon mustard, or to taste
salt to taste
freshly ground black pepper
1 pound mussels
1 pound vermicelli

Bring a large pot of salted water to a boil. Add the pasta and cook until al dente, about 2 minutes. Drain.

Meanwhile, in a large sauté pan over medium-high heat, add the mustard seeds and shake the pan to keep them from burning. Once they begin to pop (like popcorn), lower the heat and add the olive oil and onions.

Cook the onions for about 5 minutes until they turn golden, then add the garlic and cook until the garlic begins to soften. Add the tomatoes, stock, and if desired, the Dijon mustard. Simmer for about 5 minutes for the flavors to blend.

Rinse the mussels and remove the "beard" on the side of the shell. Add the mussels to the tomato sauce and turn up the heat to medium. Cook the mussels in the sauce until they open, about 3 minutes. Transfer the pasta to a warm bowl and serve with the sauce. Serving Size: about 2 cups
References :

Check out this link for a really nice recipe… "mussels with garlic butter".
I hope this helps.
References :
epicurious.com