1/3 cup extra-virgin olive oil
1 medium onion, chopped
6 garlic cloves, finely chopped
3/4 teaspoon dried hot red pepper flakes
1/4 teaspoon dried oregano
1/3 cup dry white wine
1/3 cup bottled clam juice
1 lb linguine
2 lb small cockles (up to 1 inch across; 5 to 6 dozen), scrubbed well
2 tablespoons cold unsalted butter, cut into small pieces
1/3 cup chopped fresh flat-leaf parsley
Accompaniments: extra-virgin olive oil for drizzling; dried hot red pepper flakes