Bring a large pot of heavily salted water to a boil.

While waiting for the water to boil: Add the tomatoes, along with the puree or juice they’re packaged with, into the bowl of a food processor or blender. Process several seconds, until smooth.

Heat the oil in a medium (3 Quart) saucepan. Add the garlic, fennel, and onions and cook 5 minutes or until softened. Add the pureed tomatoes, saffron, and vanilla. Reduce the heat to low and let simmer at least 15 minutes.

Once the water comes to a rolling boil, add the pasta and cook according to the directions on the package. Steam the mussels in a separate pot. When the pasta has finished, stir 1/2 cup of the cooking liquid and 1/4 cup of milk into your sauce. Drain the pasta.

Add the butter and stir until it melts into the sauce. Serve sauce over pasta and mussels.