Preheat oven to 375 degrees F and lightly spray the bottoms of a 12-cup muffin pan with non-stick spray.

In a medium mixing bowl, combine the tuna, mayonnaise, celery, onion, ground pepper and salt. Set aside.

Unfold the pastry dough on a clean, dry countertop. Using a small rolling pin, gently roll out the creases and ensure that the edges are even and symmetrical. (The puff pastry is usually heavily floured but if needed, add a little extra flour to your countertop to prevent sticking.)

Place cheese slices on top of pastry, leaving one inch bare at the top edge. Cut or tear as needed to fill in spaces, but do not overlap slices.

Spoon the tuna mixture onto the cheese and spread evenly across the cheese, leaving the top one inch bare.

Starting with the edge closest to you (the bottom), slowly and evenly start to roll the edge in and upwards and continue until the roll is complete (Filling may push its way up to the edge as you are rolling. That is okay.)

Using a very sharp, straight-edge knife, make 12 even slices (about ¾ - 1 inch wide).

Gently reshape each slice and place them into the individual cups of the prepared muffin pan.

Bake in the preheated oven for 15-17 minutes. Remove from oven and let rest for 5 minutes.

Using a butter knife, slide around the edges to release any stuck cheese, gently pop out and place the rounds on a cooling rack lined with several paper towels.

Serve with chips or fresh crudité.