Wash the mussels in fresh water.
Take a deep oven pan and add some oil and salt.
Add one sliced onion, 2 cloves of chopped garlic and parsley.
Add 1/3 of the tomatoes cut in pieces.
Sprinkle with pepper and cheese.
Add half of the potatoes cut in round slices about 1/2 inch thick.
Repeat the condiment process with onions, garlic, parsley and another 1/3 of the tomatoes.
Deposit the mussels, shell and fruit, on top of the potatoes and sprinkle with pepper as desired.
Spread the rice over the mussels and sprinkle with pepper as desired and cheese.
Cover the mussels with the remaining potatoes.
Cover the potatoes with the remaining garlic, onion, parsley, tomatoes. Again add pepper as desired.
Add one last sprinkle of cheese.
Set the oven at 375F.
At the same time put the pan on the stove and fill the pan with hot water up to the rim of the pan.
Cook the entire content of the pan until the water in the pan comes to a boil.
Once the water comes to a boil, put the pan in the oven and cook for 45 minutes.
Monitor the water level in the pan, if it get too dry add some boiling water.