In a large pot, heat the olive oil over medium-high heat, then add the garlic and shallots and cook until they soften, about 3 minutes. Make sure the garlic does not burn.
Add the red pepper flakes and tomatoes. Sauté until the tomatoes are slightly softened, then add the wine and mussels and stir to coat. Cover the pot with lid.
Heat until the mussels are cooked through and have opened, approximately 8 minutes.
Add the heavy cream, butter, and salt and pepper to taste. Stir thoroughly to coat the mussels in the cream sauce.
Bring to a simmer, then turn off the heat and add the parsley.
Spoon the mussels into a shallow bowl, discarding any mussels that have not opened. Serve immediately.