Heat the oil in a large deep, pot over medium heat. Bring the oil to 325 degrees F. Regulate the temperature with a candy thermometer. Keep the potato sticks in a bowl of water to prevent browning before frying. Remove to paper towels and dry well before placing in the oil. Working in batches, fry the potatoes until they are cooked through and tender but have no color, 4 to 5 minutes. Be sure the fries have plenty of room and gently swish them around as they are cooking. Remove them from the oil and put them immediately on a paper towel-lined baking sheet.
Preheat the oven to 300 degrees F and raise the temperature of the cooking oil to 375 degrees F.
In a medium bowl, combine the flour, cayenne, seafood seasoning, baking soda and a pinch of salt. Make a well in the center of the flour mixture and gently stir in the cold beer. Mix until just combined. When the oil is preheated to the correct temperature, dip the fish in the batter mixture. Coat the fish generously. When adding the fish to the oil, dip about 1/3 to 1/2 of the fillet into the oil and allow the batter to start puffing and then gently slide it into the oil completely. Fry the fish until they are golden brown and crispy, about 5 minutes, turning the fish over during the cooking time. When the fish are done, remove from the oil and put immediately on paper towels to blot the excess oil. Arrange the fish on a baking sheet lined with a cooling rack. Hold the fish in the preheated oven until serving. Work in batches and be sure not to crowd the oil.
Again, working in batches, fry the fries a second time at 375 degrees F, until they are golden brown and crispy. Remove them from the oil, immediately put them on paper towels and toss with salt. Transfer the fish to a serving platter and serve with the fries.