Place the ground beef in a large pot and pour in enough water to cover beef. Boil until beef is cooked through. Drain.
Add water to cover cooked beef, add onions and enough bouillon granules to taste. Cook until the onions are soft. Season with salt and pepper to your taste and make sure the filling has enough bouillon to have a nice beef flavor.
Combine the 1/4 cup water with the cornstarch and stir until smooth. Add to the beef mixture and cook until mixture has thickened. Allow to cool to room temperature.
Preheat oven to 375 degrees F (190 degrees C).
Roll out pastry to fit a 9-inch pie plate.
Pour beef mixture into the pastry crust and cover the top with pastry. Crimp edges and prick top.
Bake in preheated oven until pie crust is lightly browned, about 40 minutes.