Preheat oven to 325 degrees. In a mixing bowl, combine milk, egg yolks, orange juice and zest; mixing well. Pour into pie crust and bake for 35 minutes, or until toothpick inserted comes out clean. In a small bowl, combine cream cheese, sugar, sour cream and extract until smooth. Spread evenly on pie and return to oven for 10 minutes. Cool, chill 4 hours before serving. Serves 8.