Directions
Step 1
Finely mince the parsley and garlic by hand or in a small food processor; set aside.
Step 2
Using a mandoline, the slicing side of a box grater, or your food processor’s 4mm slicing blade, slice the potatoes into 1/8-inch slices. Repeat with the onion. Halve the cherry tomatoes (if they’re large, quarter them).
Step 3
Pick over the mussels and throw out any that don’t stay closed or have a broken shell. Rinse the rest under cold water and pull off any beards. Heat a large frying pan or stockpot over medium-high heat. When hot, add 2 tablespoons olive oil and the mussels in one layer (work in batches if needed). Cover (a see-through lid is best) and cook until the mussels start to open, between 3 and 5 minutes. Use tongs to transfer them one at a time to a large bowl, leaving as much of their liquid as possible in the pan. Throw out any mussels that don’t open.
Step 4
Leave the mussels on the shell half they’re still attached to and remove and throw out the other halves, placing the mussels into another bowl or a platter as you work. Drizzle the mussels with 2 tablespoons olive oil and cover with a plate or clean dishtowel so they’ll stay moist.
Step 5
Place the liquid from the pan into a 4-cup measuring cup. If it looks sandy, drain it into the cup through a strainer lined with cheesecloth. Add in any liquid that collected when you were separating the mussels; set aside.
Step 6
Preheat the oven to 425°F. Drizzle 2 tablespoons olive oil into a round baking dish 3 inches deep and 12 inches in diameter, or a 13×9 rectangular baking dish. Start layering the ingredients: Place
a layer of potatoes on the bottom of the baking dish, then top with half the onions. Scatter on half of the cherry tomatoes and half the garlic-parsley mix, a third of the grated cheese, and half the black pepper. Carefully nestle in the mussels on their half shells, meat facing up. If any liquid collected while the mussels were resting, add it to contents of the measuring cup; then add enough water to make
3 full cups.
Step 7
Top the mussels with an even layer of rice. Scatter on the remaining cherry tomatoes, onions, garlic-parsley mix, and black pepper. Make a top “crust” with the rest of the potatoes, placing them in an overlapping pattern to seal in the other ingredients. Carefully pour the mussel liquid down one side
of the dish or in one corner if your baking dish
is a rectangle. You may not need all the liquid: It should just barely reach—not cover—the top layer of potatoes (if you don’t have enough liquid, add more water). Sprinkle on the remaining cheese and drizzle on the final 2 tablespoons olive oil.
Step 8
Cover with a tight-fitting lid or foil and bake for 50 to 60 minutes. Remove the cover or foil and taste a few grains of rice. If not yet al dente, return to the oven for 15 minutes more, then test again. When the rice is just about cooked, take off the lid or foil and return the dish to the oven for another 15 minutes or until the rice is fully tender, the liquid has evaporated, and the top layer of potatoes is golden and crispy. If you’d like it more golden, place under the broiler for 3 to 5 minutes, watching carefully.
Step 9
Out of the oven, let the tiella rest for at least 30 minutes for the flavors to meld. Use an oversized spatula to dish out servings. While you can eat it with a fork, feel free to pick up the mussel shells and lap up their contents.
