Created by Mikekey on July 12, 2015
Step 1: Prepare pie shell according to package instructions, or make your own and bake.
Step 2: Preheat oven to 300 degrees F (150 degrees C). Place the pie crust in its plate in a large, shallow baking pan lined with foil in case of a boil-over.
Step 3: Bring maple syrup to a boil in a heavy saucepan over medium heat, and cook for 5 to 7 minutes, to reduce syrup down by about one-quarter.
Step 4: Stir in cream, bring the mixture to a simmer, then remove from heat.
Step 5: Whisk egg yolks and egg together in a large bowl. Very gradually add the cream mixture to the eggs, about 1/4 cup at a time, whisking constantly.
Step 6: Stir in salt, vanilla extract, and vinegar.
Step 7: Pour the batter into the prepared pie crust.
Step 8: Bake until the pie is mostly set but jiggles slightly when moved, about 1 hour.
Step 9: Let cool before serving.