Heat oil in large skillet over medium heat. Add onions and carrots and sauté until vegetables have softened, but not browned, 8 to 10 minutes. Add beef, cinnamon, salt and pepper, stirring to combine. Cook until beef begins to brown, about 10 to 15 minutes. Let mixture cool completely.
While beef is cooking, split puff pastry in half if it’s in one piece. Roll out each piece with a floured rolling pin to roughly 9 x 11 inches. Line an 8- or 9- x 11-inch baking dish, or a shallow 2-quart gratin dish, with 1 piece of pastry, pulling up the dough to cover the sides of baking dish.
Whisk 2 eggs and add to cooled beef mixture. Spoon mixture over pastry and top with chopped parsley and dill. Top with remaining piece of pastry, pinching together the sides of both pieces of pastry. Chill in fridge for at least 1 hour (and up to 4 hours) or freeze for 15 minutes.
Heat oven to 400 degrees. Whisk remaining egg and brush over pastry. Sprinkle with sesame seeds. Bake until golden on top, about 40 minutes. Allow to cool 15 to 20 minutes before cutting. Pastel may appear wet when removed from oven, but pastry will absorb the moisture as it sits.