This is best made with fresh, not frozen, blueberries.
3/4 cup sugar
2 1/2 tablespoons cornstarch
1/4 teaspoon salt
1/4 teaspoon cinnamon
2/3 cup water
5 cups fresh blueberries, divided use (see bold/underline in recipe)
1 teaspoon vanilla extract
2 tablespoons butter (not margarine)
2 teaspoons freshly squeezed lemon juice
1 teaspoon finely grated lemon zest (yellow only, not white part)
10-inch pie crust, blind baked and cooled
In a medium saucepan, combine sugar, cornstarch, salt and cinnamon. Blend in water and 1 1/2 cups blueberries. Bring to a boil, stirring and smashing half the berries deliberately (use a potato masher a few swipes if you like). Boil, stirring constantly, until mixture is very thick, a minute or so. Remove from heat and stir in vanilla extract, butter, lemon juice and lemon zest. Cool. (See note below.)
Fold in 2 1/2 cups blueberries, coating them well. Scoop into cooled baked pie shell. Arrange remaining 1 cup of fresh berries over top. Cover with plastic wrap and chill at least 2 hours, or overnight if needed.
Serve plain, or with whipped cream, vanilla ice cream or frozen yogurt. To serve, remove pie from refrigerator and allow to come to room temperature. Sift powdered sugar over top for pretty.
Note on cooling the filling:
A quick way to cool the filling before adding the rest of the blueberries is to fill a large salad-type bowl with ice and water. Partially submerge the pan with the cooked blueberries in this cold bath, stirring every once in awhile, and in 5 or so minutes it will be sufficiently cooled to continue with your recipe. You can also just set the pan on an unused burner while it cools off, but the cold water bath is much faster and lets you get your pie in the refrigerator more quickly if time is important.