Start by rinsing your cod fillets under cold water, then pat them dry thoroughly with paper towels.

In a deep pot or heavy skillet, pour enough vegetable oil to cover the fish by about two inches and heat to 350°F (175°C).

In a mixing bowl, combine all-purpose flour with spices; slowly add cold sparkling water or beer and whisk until it just comes together.

Dip each cod fillet into the batter, ensuring it's fully coated, then lay them gently on a plate or tray.

Lower one or two coated cod fillets into the oil and fry each side for 4-5 minutes until golden brown and crispy.

Toast brioche or potato buns in a skillet until warm and golden brown, then set aside.

Assemble the sandwich with a piece of fried cod on the bottom bun, add lettuce, tartar sauce, and top with the other bun.

Serve immediately with lemon wedges on the side.