Clean the mussels under cold water, removing dirt, sand, and any mussels that are cracked or open.

In a pot, add ¼ cup of water and steam the cleaned mussels for 3-4 minutes until they open.

Mix together butter, garlic, Parmesan cheese, parsley, lemon zest, salt, and pepper in a bowl.

Remove mussels from the pot, arrange on a baking sheet, discarding empty shells and loosening the mussels from their bottom shells.

Spoon the garlic butter mixture over each mussel, then broil for 2-4 minutes until golden.

Remove from the oven, garnish and serve immediately with crusty bread.