Bring a large pot of water to a boil.
Meanwhile add mussels to a large bowl of cold water. Add a generous sprinkle of salt and allow to soak for 10 minutes. Drain well. Scrub the shells and debeard the mussels, as needed.
Add mussels and wine to a large saute pan over medium high heat. Cover and steam just until mussels have opened up. Discard any mussels that did not open. Scrape out the meat of all opened mussels and discard shells. Strain mussel broth and set aside.
Generously season boiling water with coarse sea salt. Cook paccheri according to the package instructions until slightly softened but still firm, about 10 minutes.
Add 1 cup (227 grams) reserved mussel broth, olive oil, candied tomatoes, and red pepper flakes to a large saute pan. Transfer the cooked pasta over to the saute pan (reserve the pasta water). Turn heat to high and saute the pasta while vigorously stirring with a wooden spoon.
Add a ladle (about ¼ cup or 60 ml) of pasta water (pour along the outside of the saute pan not directly on the pasta) and continue vigorously stirring. Repeat this process two to three additional times, adding more pasta water when you hear sizzling until a creamy sauce forms and the pasta is al dente.
Add mussels back in and cook just until warmed through, about 60 - 90 seconds. Turn off the heat and toss pasta with pecorino. Taste and season as needed with salt and pepper.
Serve immediately. Optionally, garnish with parsley.