Bake the puff pastry cups according to package instructions (about 18 minutes). As soon as they come out of the oven, use the end of a wooden spoon to poke down the middle of each pastry.
In a medium bowl, chop up the eggs and then use a fork to mash. Add mayonnaise, onions, salt and pepper. Stir to combine.
to assemble, place a piece of salmon inside of each cup (let it peek over the side of the cup, as shown in the photo). Use a small spoon to fill the cup with egg salad. Pile it up on top. Garnish with dill.
Keep these refrigerated until ready to serve. If it's going to be more than a couple of hours, place them in a covered container. They should be served the same day that they are assembled.
Notes
My favorite method of hard boiling eggs: place eggs in a large saucepan with cold water. Bring to a boil, then cover, remove from heat and let sit for 15 minutes. Cool and then peel.