Heat oil in wide-bottomed pot set over medium-high heat. Add onions and garlic and cook 2 minutes. Add stock, sliced sausages and parsley and bring to a simmer. Add clams, cover, and cook just until they open. (Discard any clams that do not close when squeezed before cooking, or do not open after cooking.) Serve over pasta or rice if desired.
Serves 4 as an appetizer or light lunch or dinner.