Clean mussels in cold running water. Remove any beards with a knife. Lightly tap any open mussel at the hinge to see if it closes. If it doesn’t, discard it. Discard any ones with broken shells as well.

Add 1 tablespoon of butter to a large wide pot. Add the onion and garlic. Saute until translucent and fragrant. Add the wine and chicken broth. Bring to a boil and add the mussels. Cover with a lid, and reduce the heat to medium. Cook for 5 minutes, or just until the mussels open. Shake the pot once in a while to ensure even cooking.

Add the tomatoes, parsley, butter, and lemon juice. Season with salt and pepper. Give the mussels a gentle stir. When the butter melts, fish the mussels out with tongs onto your serving bowl. Discard any mussels that didn’t open. Pour the sauce over the mussels and serve with crusty bread or pour over pasta.