1. Bring a large pot of water to a boil.
2. Heat a large saucepan over a low flame and add oil. When the oil is hot, add the garlic. Cook for about 5-10 minutes, or until the garlic begins to look translucent. Do not brown. Add the parsley and anchovy paste and cook for 2 minutes, stirring constantly.
3. Raise the heat to medium high and add the clams and white wine; bring to a boil. Cover the pan and steam the clams for about 7-10 minutes, or until they open up.
4. At this point, add the pasta to the pot of boiling water.
5. When the clams have opened, remove them from the pot and shuck all but 16 of them. Return the shucked clams to the pot, and set aside the remaining 16.
6. Cook the pasta until tender. Drain and add to the pot with die clams. If desired, add the butter. Toss well and divide among 4 plates. Garnish each with 4 clams in the shell.