Sometimes, the issues with cooking mussels are logistical. Is your pan big enough to hold enough of them to feed a hungry table? Is it wide enough so they will cook evenly? And how long will the inevitable steam hang around in the kitchen?
The solution to all those seems to be the oven-steaming method in this recipe. Four pounds of bivalves fit nicely into one large or two smaller roasting pans. With a tight lid of aluminum foil, they steam in about the time it takes for you to crisp the pieces of bacon and saute the ribbons of leeks that will go on top. (Cooking those topping separately, by the way, ensures their proper textures.)
The recipe also includes a prep step that should become a habit: an ice-water soak for the mussels and for the leeks. Grit will fall away and stay away, as long as you lift those components out of their baths.