Preheat oven to 400 degrees. Roll out the puff pastry on a lightly floured surface to fit the sheet pan.
Place the silpat into the sheet pan. Place the puff pastry on the silpat in the pan, curving the pastry up the edges of the pan. Prick the pastry all over with a fork.
In saute pan, heat olive oil over medium heat. Saute asparagus and leeks for 3 minutes. Remove from heat and set aside.
In a large bowl, mix eggs, cottage cheese, salt and pepper.
Scatter asparagus, onions, and goat cheese on pastry. Pour egg mixture evenly over pastry and sprinkle parmesan evenly on top.
Bake 10 minutes. Lower oven temperature to 375 degrees and bake until crust edges are golden and eggs are set and lightly browned (approximately 25 minutes).
Run a butter knife around the pan edges to loosen crust. Garnish with dill (if desired).