Step 1
Preheat the oven to 350 degrees F (175 degrees C). Lightly grease a 9-inch deep-dish pie plate.
Step 2
Season venison with garlic powder onion powder salt and pepper. Mix in flour to coat pieces. Combine egg and milk in a small bowl for egg wash and set aside.
Step 3
Heat olive oil in a medium saucepan over medium heat. Add onion and garlic; saute until soft and translucent 5 to 7 minutes. Turn heat to high and add venison; quickly brown the meat while stirring making sure not to overbrown 1 to 2 minutes. Remove mixture into a bowl and set aside.
Step 4
Make gravy by deglazing the pan with red wine and Worcestershire sauce scraping the browned bits from the bottom with a wooden spoon. Reduce until the pan is almost dry 10 to 15 minutes. Reduce heat to low and add beef broth. Dissolve cornstarch with water in a bowl and pour into the broth whisking constantly. Bring to a simmer and reduce heat; cook until thickened about 5 minutes.
Step 5
Meanwhile fill a large bowl with ice and cold water. Bring a large pot of lightly salted water to a boil. Add potatoes carrots and celery and cook uncovered for 2 minutes. Drain in a colander and immediately immerse in ice water for several minutes to stop the cooking process. Drain.
Step 6
Combine drained vegetables with venison mixture corn and peas in a large bowl. Mix thoroughly.
Step 7
Line the prepared pie dish with 1 pie crust trimming edges if needed. Place venison mixture into the pie crust pour gravy over the top spread mushrooms over and cover with the other pie crust. Brush on egg wash and cut vents in the top.
Step 8
Bake in the preheated oven until the crust is golden brown and you can see filling is bubbling 45 minutes to 1 hour. If edges of crust are getting too dark cover edges with aluminum foil until center crust has caught up. Let cool for 5 minutes before serving.