Preheat oven to 400 degrees. Grease a round pie dish. Gently pat one sheet of puff pastry into the greased pie dish. Set aside.
Prepare the homemade cream of chicken by melting 6 tablespoons butter in a medium sauce pan over medium-high heat. Stir in the flour for 1 minute. Gradually whisk in broth and milk. Stir in salt, pepper, and garlic powder. Once thickened and smooth, remove from heat.
In a large skillet melt the 2 tablespoons of butter. Stir in mushrooms and minced garlic for 2-3 minutes til garlic is fragrant and mushrooms begin to brown.
Stir in chicken and bacon for 1 minute, then stir in cream of chicken and cheddar cheese.
Transfer mushroom and chicken mixture to your pie dish. Cover with remaining sheet of puff pastry (it doesn't have to cover all the edge of the pie dish, just line up the corners with the corners of the bottom puff pastry sheet).
Brush whisked egg all over the top crust.
Bake on bottom rack for 25 minutes til crust is puffed and golden brown. Cool slightly before serving.