In a saucepan, whisk together milk, 2 cups maple syrup, and egg yolks.
In a bowl, sift together flour and cornstarch. Gradually whisk flour mixture into milk mixture. Stir in 2 teaspoons vanilla. Heat to boiling, cooking for 8 minutes, or until very thick, stirring constantly.
Pour into prepared crust. Refrigerate.
In another bowl, whip cream with sugar and remaining ½ teaspoon vanilla. Spread over chilled pie. Refrigerate.
Preheat oven to 375°F. Line a rimmed baking sheet with aluminum foil. Set a cooling rack on foil. Arrange bacon slices across rack in rows, not overlapping.
Whisk together remaining ¼ cup maple syrup and mustard. Generously spoon over bacon. Bake for 12 to 15 minutes. Turn over bacon slices and baste again. Bake for 5 to 10 minutes more, or until bacon reaches desired crispness. Remove from oven and sprinkle with freshly ground black pepper. Set aside for 5 minutes. Coarsely chop cooled bacon. Sprinkle on top of pie.