Set a 30cm/12” wide deep saute pan or wide pot over medium-high heat; add the olive oil, parsley stems and garlic cloves.
When the parsley and garlic just begin to be surrounded by sizzling bubbles, add the mussels, with just the water left clinging to them from washing. Cover the pan.
When all the mussels have opened, remove the pan from heat. Prop the pan up at an angle and pick the mussels out into a bowl. Pour the juices into a separate bowl, being careful not to let out any sand you’ve trapped in the corner of the pan (which is why you propped it up – smart right??). If you’re worried about this, you can strain the juices through a moistened paper towel. Discard the garlic and parsley stems. See notes at the end for two bonus recipes that pick up from the end of this step.
Remove the mussel meat from the shells except for two or three per serving that you’ll use for decoration. Add the shelled and whole mussels to the bowl with the juices to keep them moist.
If using canned tomatoes, drain the juice away and save it for another use (I add ice, lemon and sparkling water to it and drink it – I have heard some people add vodka :) ). Then, you can crush them with your hand, chop them with a knife, run them through a food mill, or, what I usually do, leave them in the can after draining and run a stick blender down the height of the can one time (this leaves quite a bit of texture). Each will give you a slightly different effect. I do not recommend using passata (tomato puree) unless it’s homemade. The texture of most commercial passata is too liquid and it rarely has as good a taste as whole peeled tomatoes, even from the same brand.
If using small fresh tomatoes, cut them in half or quarters depending on your taste and their size. If they are watery, you can pick out the seeds and water with your pinky (try not to squeeze them)
Put 6 quarts or liters of water in a large pot over high heat.
Wipe out the skillet from the mussels with a wet paper towel. Add the oil and garlic and place the skillet over medium heat.
Stir in most of the mussel juice and cook for a minute or two to blend. Turn off the heat.
Add the pasta. DO NOT BREAK THE PASTA IN HALF. Stir the strands until they are completely submerged. Continue stirring often so the pasta does not stick to the bottom. This becomes less important the closer the pasta is to being done.
Remove the pan from the heat. Empty the pan into a warm serving platter, or scoop and twirl individual portions onto individual plates or bowls, with two or three whole mussels in the shell going on top of each portion.
Whether over the whole serving platter or each plate, drizzle over fresh extra virgin olive oil and grind abundant black pepper.
Bonus recipe: ‘nzuppa ri cozzuli (Italian cognate: zuppa di cozze) or simply mussel soup: to serve them as they are at the end of step 6, combine the mussels & their juice in a warm serving platter or individual bowls. You could optionally season the juices before or after cooking the mussels with chopped parsley, and/or chopped fresh tomato or a spoonful of tomato sauce or (good if not very Sicilian) grated lemon peel.
Bonus recipe #2: If you add abundant freshly ground pepper to the preceding dish, you have pipata ri cozzuli (impepato di cozze) – or an “in-peppering” of mussels.
As a main course, figure on 1.5 pounds / 700-800g of mussels per person, or half that for an antipasto. In either case, abundant crusty bread is a must – if it’s semolina bread with sesame seeds, so much the better.