Peel the potatoes and cut them into sticks.
Soak the raw fries for 10 minutes in cold water to remove the excess starch.
Remove them from the water and dry with paper towels or a clean cloth.
Heat the frying oil.
Cook the fries for 10 minutes. Do this in two batches.
Drain and repeat with the other half the potatoes.
Scrape the mussels and wash them 2-3 times.
Drain and place in very cold water for 20 minutes.
Remove the mussels that rise to the surface, are opened or broken. They are not safe to consume.
Peel and finely slice the shallots.
Chop the parsley and peeled garlic.
Melt the butter in a large heavy pan.
Add the shallots and sauté for a few minutes.
Add the garlic, parsley and mussels to the pan.
Drizzle with the white wine and pepper.
Cover and cook over high heat for 6 to 7 minutes, stirring occasionally.
Meanwhile reheat the frying oil.
Return the fries to the oil for another 5 minutes.
Discard any mussels that have not opened after the cooking time.
Serve immediately with the mussels.