Make the tuna salad

• Drain the tuna and flake it into a bowl.
• Add the mayonnaise, Dijon mustard, diced pickles, red onion and celery.
• Season with salt and black pepper and mix until combined.

Melt the cheddar into shells

• Heat a non-stick pan over medium heat.
• Scatter the shredded cheddar in an even round and let it melt and turn crispy.
• While still pliable, drape the cheese over an upside-down glass or mold to form a taco shell shape and let it set.

Fill and serve

• Spoon the tuna salad into the crispy cheddar shells.
• Serve immediately while the shells are crisp.