Rinse and scrub the mussels under cold water. Remove any beards and discard any mussels that are open and do not close when tapped.
In a large pan or pot, heat a generous drizzle of olive oil over medium heat. Add the diced shallot and sliced garlic, cooking until fragrant and slightly golden, about 2 minutes. Stir in the crushed red pepper flakes.
Add the chopped plum tomatoes and the passata to the pan. Season with salt and black pepper to taste. Simmer for about 5–7 minutes, stirring occasionally.
Increase the heat to medium-high. Add the white wine to the sauce and bring it to a gentle boil. Add the cleaned mussels to the pan. Cover and cook for about 5 minutes, or until all mussels have opened. (Discard any that do not open.)
While the mussels are cooking, bring a large pot of salted water to a boil. Cook the spaghetti according to package instructions until al dente. Reserve about ½ cup of pasta water, then drain the pasta.
Add the drained spaghetti to the pan with the mussels and sauce. Toss everything gently to coat, adding a splash of reserved pasta water if needed to loosen the sauce.
Garnish with chopped fresh parsley and drizzle a little more olive oil over the top. Serve immediately with crusty bread if desired.