Prepare the Potatoes:

1. Wash potatoes, peel them (optional- I don't usually), and slice them into thick fries. As you cut the fries, place them in a large bowl of cold water to soak. (Why soak them? This allows some of the starches to release into the water, which then helps the inside of the fries to be more tender, and allows the outsides to crisp up better.) Set aside to soak while you prepare the batter.

Make the Batter:

1. Whisk together the flour, baking soda, and salt in a pie plate. Slowly whisk in the water until batter is smooth and thick, not so thick that it doesn't spread out flat in the dish. You want it to be about the consistency of pancake batter. Add more water if needed. Cover and set aside for 30 minutes.

First Frying (Fries):

1. Remove the fries from the water bath, and spread them out on a large baking sheet lined with paper towel. Allow to dry while the oil heats up.
2. Add enough oil to an electric skillet, or a large heavy-bottomed pan with tall sides so that it is about 2-inches deep. Heat oil to 325 degrees.
3. Dry the potatoes with paper towels as you add them to the oil. Fry in a few batches, about 10-15 fries per batch, until the fries take on a white, opaque appearance and just begin to brown, about 4-5 minutes.
4. Remove from oil and spread out on another baking sheet lined with paper towels. At this point, the fries will be soft, and somewhat soggy-looking. No worries! That's what the second frying is for.

Fry the Fish Fillets:

1. Adjust the heat so that the oil reaches 350 degrees. Dip each fillet into the prepared batter, and gently slip them into the hot oil. Fry until golden brown, about 5 minutes. Remove from oil to drain on paper towel.

Second Frying (Fries):

1. Raise the oil temperature to 375 degrees, and return the fries to the oil (larger batches are okay this time). Fry for 2-3 minutes until golden and crispy. Remove from oil and drain on fresh paper towels. Sprinkle with salt.
2. Serve immediately, with tartar sauce and ketchup.