Quebecois Maple Cream Pie

Step 1
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 2
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. Stir in cream, bring the mixture to a simmer, then remove from heat.

Step 3
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. Stir in salt, vanilla extract, and vinegar. Pour the batter into the prepared pie crust.

Step 4
Bake until the pie is mostly set but jiggles slightly when moved, about 1 hour. Let cool before serving.