Preheat oven to 400 degrees F. Move rack to center position.
In a food processor, add salmon, dill, lemon juice and cayenne pepper. Process until a coarse paste forms. Add mustard and cheese. Process until the mixture is smooth.
Lay out a sheet of thawed puff pastry (follow directions on package) on a lightly floured work surface. Use a round 2-inch in diameter cutter [in a pinch, the bottom of a dixie cup works] to cut circles from each sheet. [Original recipe calls for 30. We were able to cut 39 circles from our sheets and had enough filling to create 39 finished puffs.]
Using a mini muffin pan or tart pan, press a round of dough into each cup. Use a small form to poke 10-15 holes into the bottom of the dough.
Using a spoon, fill each cup with about 1 teaspoon of the salmon mixture. [Original recipe recommends using a pastry bag with a wide tip and piping in the filling.]
Bake puffs for 12 minutes.
Salmon may have popped up during baking. If so, press back down into pastry.
Remove puffs to a plate or serving platter. Use a skewer or two toothpicks to make a hole in the center of each puff. Place 3 pieces of chive into each hole, so they are sticking straight up. Serve.