1Move a rack to the center of the oven and preheat oven to 350 degrees F (175 degrees C).
2Stir gingersnap crumbs with light brown sugar and melted butter in a bowl until thoroughly combined. Press the mixture into the bottom and up the sides of a 9-inch pie dish.
3Bake the crust on the center rack of the preheated oven just until set, 3 to 4 minutes. Baking too long will make the crust hard to cut. Remove the crust and let cool.
4Stir cornstarch and water in a saucepan until smoothly mixed; add sugar and 1 1/2 cups blueberries. Bring to a boil over medium heat, stirring until the blueberry sauce is thickened, 1 to 2 minutes. Remove from heat and stir in remaining 2 1/2 cups blueberries and lemon juice.
5Pour filling into the gingersnap crust and refrigerate until chilled and set, at least 1 hour.
Footnotes
Cook's Note:
For 6 cups of blueberries, double the cornstarch, liquid and sugar. If using frozen blueberries, drain the juice and use in place of water.