"Preheat oven to 400°F.For the filling: Melt butter in a 12-inch skillet over medium heat. Toss in the beef, flour, salt, and pepper and cook, stirring occasionally with a wooden spoon until thoroughly browned on all sides, about 5-8 minutes. Add one cup of broth to deglaze the pan and scrape up any browned bits from the bottom of the pot. Transfer beef to a medium bowl and reserve. Return skillet to medium heat and add remaining butter. Add leeks, carrots, celery and cook until just beginning to soften. Stir in garlic and cook 1-2 minutes, until fragrant. Return beef to the skillet and stir in bay leaves, rosemary, and thyme. Simmer briefly then add Dijon, Worcestershire, horseradish, and balsamic vinegar. Stir in remaining broth and stout. Cover and transfer to the oven to braise for 60 minutes. Add potatoes and pearl onions. Cover and braise an additional 20-30 minutes (or until the potatoes are tender and the gravy is thickened). Remove skillet from the oven and add peas and season to taste with additional salt and black pepper, if desired. Remove and discard herbs. Allow filling to cool while preparing crust. For the crust: Roll out the bottom sheet of puff pastry and sprinkle Irish cheddar on top. Add a second layer of puff pastry and roll them together into one 10x12-inch rectangle. Cut into 1-inch strips for lattice design or small rectangular cutouts. Freeze until filling is cooled and pot pie is ready to bake. Top skillet with prepared pastry and brush with egg wash. Bake (400 degrees) on the bottom rack of the oven until the crust is crisp and golden brown, 35 to 40 minutes. Let rest about 10 minutes before serving and garnish with fresh parsley."