• Step 1: Preheat your oven to 400°F (200°C). Cut the potatoes into wedges and toss them with 2 tablespoons of oil, salt, and pepper. Spread the potato wedges on a baking sheet and roast for 25-30 minutes, flipping halfway, until golden brown and crispy.
• Step 2: In a medium bowl, whisk together the flour, baking powder, and salt. Gradually whisk in the cold soda water (or beer) until the batter is smooth and free of lumps. Let the batter rest for 10 minutes.
• Step 3: In a large, heavy-bottomed pot or Dutch oven, heat 2 inches of oil to 350°F (175°C). Pat the fish fillets dry with paper towels and season them with salt and pepper.
• Step 4: Working in batches, dip the fish fillets into the batter, allowing any excess to drip off. Carefully lower the battered fish into the hot oil and fry for 3-4 minutes per side, or until golden brown and crispy. Drain the fried fish on a paper towel-lined plate.
• Step 5: Serve the crispy fish and roasted potato wedges immediately, garnished with lemon wedges and tartar sauce on the side. Enjoy your homemade fish and chips!