This was always a favorite of mine as a kid - and I loved taking leftovers to school the next day for lunch and eating it cold (with a little malt vinegar). I had given up making my own pastry crust years ago when the shortening I always used was discontinued. I recently found this pastry recipe and am now back to making it from scratch. So much better! Use your favorite pie crust recipe or the one here.
Place flour, salt, shortening and butter in a large bowl. Use a pastry cutter, forks or your fingers to mix the butter and shortening into the flour until the pieces are no larger than a pea.
Add about half of the cold water and mix together. Add more water until your dough holds together well. Divide the dough in half. Roll out each half into a 8-9" circle.
Peel and grate potato. Place in a bowl with salted water to cover and set aside.
In a large saute pan, add 2 T butter and melt over low heat. Add onions, garlic and thyme and cook very slowly until the onions begin to caramelize. Add the white wine and and cook until the liquid is gone - about 20 minutes. Add salt and pepper to taste. Place in a bowl and set aside.
Cut steak into bite sized pieces. Turn up heat under saute pan to high and add steak, in batches if necessary, to sear. Season with salt and pepper. Stir - just to get some color on the meat - cooking about 3 minutes. Remove to a plate.
Place one rolled out pie crust in a pie plate. Trim the edges on HALF of the crust to be just at the edge of the pie plate.
Drain the water off the potatoes and squeeze the water out by hand. Fill half of the crust with half of the potato.
Add half the steak.
Cover with half of the onion mixture.
Fold the crust back over the contents. Flip the pie dough under the trimmed edge and crimp.
Repeat with the other disk of pie dough.
Cover and crimp. Brush the top with egg wash.
Bake at 400 for 45-55 minutes. Let set 5-10 minutes before cutting into the pasty.