Purchase pre-made pastry or make your own by combining flour and salt. Then cut in shortening (or butter) until crumbly. Add water a little at a time until dough is not too dry and not too wet. Wrap in plastic or place in a covered bowl. Set in refrigerator while making the pot pie mixture.
Prepare pot pie mixture, by chopping/shredding ingredients.
Toss beef with salt, pepper, garlic, and flour.
Melt butter on medium-high heat and seer beef along with onion.
Add beef stock, milk, and Worcestershire. Mix to combine.
Stir in chopped vegetables and cook for 20 minutes.
Roll pastry dough. Find a bowl with a circumference similar to the tart size to cut circles in the pastry. Roll the dough out a bit more after cutting the
circle out to lay better in the tart pan. Cut circles for top and bottom of each mini pot pie.
Add dough to the tart pan, fill with pot pie filling. Add top. Crimp edges.
Poke two holes in the top of each and brush egg yolk on pastry tops.
Bake at 425° for 30 minutes.