-
Once the pie has chilled, make the topping.
-
Stir together the sugar, cornstarch, water, and lemon juice in a small saucepan until well combined. Add the blueberries and stir to coat.
-
Set the pan over medium heat and cook, stirring frequently, until the mixture boils and thickens quite a bit, about 10 to 20 minutes. (At first the mixture won’t seem to be doing much, then the blueberries will give off a lot of juice, then the mixture will start to thicken.)
-
Remove from the heat and cool to room temp. Spread over the pie and chill for another hour or so, until the topping is fully chilled.
-
Slice and serve.
-
Uneaten pie can be stored in the fridge, covered, for 3 or 4 days. You can also freeze individual slices, tightly wrapped, for about a month.