This garlicky, addictive dish is best served with crusty bread or a bowl of pasta. I personally prefer placing pieces of bread at the bottom of my bowl and spooning the sauce and mussels on top. That way, the bread soaks in the flavorful tomato sauce, softening the hard crust to make that perfect balance of crunchy and squishy (in a good way).
To make this dish extra garlicky, I roasted garlic while making my sauce and spread it on the toasted bread right before serving.
Preheat the oven to 350 degrees. Remove the top of the head of garlic and drizzle oil and a pinch of salt on top. Wrap in foil and place in the oven for 35-40 minutes.
Heat a large pan over high heat; when hot, add the oil and turn the heat down to medium. Add the shallots and season with salt and pepper, stirring constantly, until softened, about 7-8 minutes. Add the garlic and cook for 2-3 minutes, until lightly browned. Add the tomatoes, turn the heat to high and then bring to a simmer for about 30 minutes. Season to taste with the chile flakes, salt, and pepper, stirring occasionally.
When the sauce has reached desired consistency, add the mussels and cover with a lid, until their shells have opened, about 3-4 minutes.
Meanwhile, remove the garlic from the oven and toast the bread, if desired. Discard any mussels that have not opened and serve alongside the bread and roasted garlic, leaving guests to spread it on as they want.