Though the taste of fresh mussels may be slightly better, but frozen ones sold in supermarkets are almost ready to eat, and so it saves you a lot of time and effort in preparation work.
Heat oil in pan,fry garlic and tomatoes. add in seasonings and some water, and let simmer over low heat for about 3 minutes. turn on high heat, and add in mussels and stir well until mussels are cooked.