To braise your beef, preheat your oven to 150°C. Brown your meat (2-4 minutes). Remove and caramelized your vegetables. Add then add the brisket back to the crockpot along with your stock, wine, vinegar, herbs, and garlic. Cover with butchers paper or baking paper. and cook for 2 ½ half hours. Once cooked remove from the oven, drain (set aside this liquid), and cover your brisket.
Once cooled cut your brisket it into 2cm -3cm cubes.
Cook your mushrooms and garlic with butter and add the flour and mustard slowly add in your cooking liquid from the brisket Cook until the mixture is light brown.
Once browned, add the leftover liquid from the brisket, and some parsley to the mushroom mixture.
If you're using frozen puff pastry, get it out of the freezer to defrost. If you're using fresh puff pastry, roll it out and cut 4 rounds of pastry.
Turn your oven up to 250°F
Fill your pie dishes and cover with the pie lids you cut out
Brush with an egg wash and pierce the top. And place in the oven.
Give them at least 30 minutes or until golden brown.