Preheat oven to 375 degrees F. Bake bottom empty pie crust (in pie pan) on cookie sheet on middle rack of oven for 17 to 20 minutes, until lightly brown.
While bottom crust is baking, chop all vegetables into ½-inch cubes and set aside. When crust is done, remove from oven and set temperature to 425 degrees F.
Cut goose breast into ½-inch slices. Place slices in a bowl and coat well with olive oil, pepper, sage, and thyme. (You don’t need to add salt if you have brined the breast. For brining instructions, see below.) Mix until seasoning is distributed evenly. Set aside.
Sauté vegetables in butter, with salt and pepper to taste, in a cast iron pan until tender but firm. Remove from heat, pour vegetables into a medium-sized bowl, and set them aside.
Using the same pan, set the heat just below high and sear the goose pieces in olive oil quickly, then remove. Place meat in bowl with vegetables and set aside.
Combine chicken broth and cream in a saucepan with cornstarch and whisk on medium heat until mixture thickens.
Scoop goose meat and vegetable mixture into cooked pie crust. Pour chicken broth-cream sauce over the meat and veggies until it is almost overflowing. Cover with top pie crust and pinch edges gently against lower crust. Cut 4 slits in the upper crust that are long enough to allow for bubbling.
Place pie in oven and bake 20 to 25 minutes or until crust is a light brown and filling is bubbling through slits. Remove from oven and let cool for 5 minutes before serving.