Pi day

On Pi day (3/14 in the USA) it is traditional to make a pie. This year was no exception. I wanted a steak and kidney, but buying kidneys is tricky, so this was steak, onion and mushroom pie. And if I say so myself it was damned good!
Ingredients
2T Beef drippings (or veg oil if no drippings)
1 1/2 lb beef chuck, cut into 3/4" cubes
4 medium onions sliced
1/2 lb mushrooms quartered
1/2 can pilsener beer
6 small yukon gold potatoes, peeled and chopped into 1/4" cubes
Salt/pepper to taste
Cider vinegar (1t or so) to brighten the flavors
1/2 package frozen puff pastry rolled to cover the pie dish
1 egg + 1t water beaten together

Method
The beef drippings are the secret inredient heat them (or the oil) in a dutch oven until smoking. Meanwhile season the meat with salt/pepper. Brown in the hot fat turning once. Set the meat aside.
Into the same pan put the sliced onions and cook until sligtly browned. About 8 minutes stirring occasionally. When the onions are cooked, add the meat and any juices bask into the pan. Pour the beer over the meat. Put the lid on and cook in a 300 oven for almost 2 hours.
Cool the dutch oven, and add the potatoes and onions to the meat/onions. When the meat mixture is cool, place in a pie dish (Pyrex if possible) and cover with the rolled out puff pastry. Make vent holes in the puff pastry. Brush with the beaten egg and place in a 425 oven for 20 minutes - or until evenly brown. Note you may have to rotate it.
After the crust is set, turn the oven down to 300 degrees and cook for 18 minutes - heating up the meat and cooking the potatoes and mushrooms.

Serving
Serve a piece of pie with some simply bolied peas.