Peel fries and chop them into ¼-inch matchsticks. Then soak potatoes in cold water for a few minutes to an hour.
Heat a large pot of oil to 325 degrees F. and blanch french fries in batches for five minutes at this lower temperature. Remove the fries after five minutes and let drain on paper towels.
When almost ready to serve, heat oil to 365-375 degrees F. and refry blanched fries for 3-4 minutes. They should turn a deep brown and get crunchy immediately.
Drain and serve with mayo.
For the mussels:
Clean the mussels by running them under cold water, scrubbing them lightly and pulling out any stuff beards that are attached to the mussels (the tiny fibers that stick out the end should just pull out).
In a large pan over medium heat, add olive oil and garlic and cook for a minute until garlic is fragrant. Be careful not to burn it.
Add in diced tomatoes, white wine, red pepper flakes, and a pinch of salt and pepper. Let simmer for 10-15 minutes.
Add mussels, cover, and cook for about 5-6 minutes until mussels are opened.
Add fresh basil and stir together. Serve immediately with mayo and fries!
For the mayo:
Whisk together yolks and mustard. Gradually and slowly whisk in oil until the mixture emulsifies into a thick dip. Season with salt and a squeeze of lemon and set aside until needed.