In boiling water, lower the mussels directly in the package, in the package (cut off the top of the package), reduce the heat and boil for 5 minutes. Transfer the finished mussels to a colander from the bag. Season with salt and pepper. Put half a lemon slice in each shell (while they are still hot). Boil the rice, roll the balls out of it (for this you need to add butter) and put in tartlets.