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In a medium saucepan, add a teaspoon of salt and the peeled and chopped potatoes, then cover with cold water.  Bring to a full boil over high heat, then reduce the heat to simmer. Cook for about ten minutes, until a fork or knife can easily pierce the potato. Drain the potatoes, then return the saucepan to the stove, stirring occasionally for about a minute until the surface moisture has steamed away. In a large bowl, mash the potatoes until smooth.  Mix the egg yolk and cream together, and blend into the potatoes along with the melted butter. Add the scallions, then salt and pepper to taste. When you're satisfied, cover and set aside while you prepare the filling. Heat 1 teaspoon vegetable oil in a heavy skillet until just beginning to smoke, and quickly brown the beef in 4 batches. When finished, set aside. In the same skillet, heat 1 teaspoon vegetable oil until shimmering, then add the mushrooms and onions. Cook 5 to 6 minutes, until the onions are just softened and turning brown at the edges. Add the garlic and tomato paste and cook for about 2 minutes. Stir in the porter, scraping the bottom to loosen the fond, and cook for about a minute, then add the flour, stirring and cooking for another minute. Pour in the stock, add the anchovy, thyme and bay leaf bundle, and carrots. When the mixture comes to a boil, reduce heat and bring the mix to a low simmer.  Stir in the beef, cooking for five to ten minutes, and continue stirring occasionally. Add in the cornstarch, and stir for another 30 seconds. Remove the thyme and bay leaf bundle, and adjust seasonings with salt and pepper, to taste. Slide the pie into the oven, and broil for 10 to 15 minutes, until the potatoes are nicely browned. Remove, let sit for for a few minutes. Garnish with scallions and parsley, and serve piping hot with a hearty ale.

Summary:
Prepare the potatoes. Mash the potatoes. Prepare the beef. Cook the veggies. Add the porter. Add the rest of the ingredients. Broil the pie.