1 pint blueberries (about 2 cups), divided
3 teaspoons Grand Marnier, divided
2 teaspoons granulated sugar, divided
1 (9-inch) ready-to-use graham cracker crumb crust
2 pints vanilla frozen yogurt, slightly softened
Combine 1 cup of the blueberries, 1 teaspoon of the Grand Marnier, and 1 teaspoon of the sugar in a small bowl. Mash with a fork or potato masher until the mixture is almost sauce-like, but still chunky.
Spread the mashed blueberries evenly in the pie crust. Top with the softened frozen yogurt and spread it out in an even layer. Cover with plastic wrap and freeze until firm, at least 3 hours or overnight.
To serve: Toss the remaining 1 cup of blueberries, remaining 2 teaspoons Grand Marnier, and 1 teaspoon sugar together in a small bowl. Let the mixture macerate while the pie stands at room temperature for 10 minutes. Serve slices with a spoonful of the boozy blueberries on top.