In a medium sized bowl, combine the flour, salt, pepper and beef cubes. Toss to coat the meat completely in the flour mixture.

 In a large skillet over medium high heat, add 3 tablespoon of oil and when it is hot add 1/3 of the beef cubes. When the beef has become a rich brown, transfer to a dutch oven or heavy- bottomed pot and continue browning the remaining batches of beef. 

When all the beef has been browned and transferred, add ½ cup of the beef stock to the skillet, scrapping up all the little bits and pour the rich sauce into the dutch oven with the beef. 

To the same skillet, add 2 tablespoons of oil and the onions and mushroom stems/caps. cook the onions and mushrooms for 6-7 minutes, until soft and then add them to the dutch oven with the beef. Add the tomato paste, thyme, beef stock and stout to the dutch oven. Bring to a boil over medium high heat, reduce the heat to simmer and gently cook with the lid on for 1-1/2 to 2 hours or until the beef tests fork tender

Preheat the oven to 425°F

Remove the dutch oven from the heat and pour the beef mixture into a large colander set over a pan or a bowl. Reserve the liquid and allow the beef mixture to cool. when cool, divide the mixture into four individual 12-ounce oven proof bowls. Pour in enough of the reserved liquid to just reach the top of the mixture but do not cover it. 

Dampen the outside rim of the first dish with some of the egg mixture. Cut the defrosted pastry into quarters and working with one quarter at a time, roll it out, cut a circle about 1 inch larger than the top of the dish (I used a lid of a saucepan as my pattern), carefully lift the circle of pastry and position it over the top of the dish, pressing the overhanging pastry against the outside of the dish continue this process with the remaining dishes of meat mixture. Brush the pastry tops of the dishes with the egg yolk mixture. Make a small cut in each pie top and place on a baking sheet. 

Place the baking sheet with the pies on the middle rack of the oven and bake for 20 to 25 minutes, turning once if necessary to brown evenly 

Remove the pies from the oven and serve immediately.