- Preheat oven to 375 degrees. In a large bowl, combine blueberries, cranberries, 1½ cups sugar, cornstarch, orange zest, orange juice, and vanilla.
- Pour fruit mixture into an unbaked 9-inch pie crust, sprinkle with slivered almonds, and dot with butter. Lay top crust over fruit and crimp edges to seal. Make a few decorative cutouts or slits in top crust to allow steam to escape. Brush with milk, then sprinkle evenly with 1 tablespoon sugar.
- Place pie on a baking sheet and bake until the filling is hot and bubbly, about 1 hour. If edges begin to brown too quickly, cover pie with foil. Let cool on a wire rack before serving.