Ingredients

• 10 ounces gingersnaps, preferably thin
• 2 tablespoons all-purpose flour
• 2 tablespoons raw sugar or granulated sugar
• 1/2 teaspoon kosher salt
• 6 tablespoons (3/4 stick) unsalted butter, melted, slightly cooled
• 2 teaspoons unflavored powdered gelatin
• 2 tablespoons plus 1/2 cup whole milk
• 2 3/4 cups plain whole-milk Greek yogurt
• 1/2 cup (packed) light brown sugar
• 1 teaspoon finely grated lemon zest
• 3 cups seedless black grapes
• 1/3 cup granulated sugar
• 1/4 cup fresh lemon juice
• 1 teaspoon freshly ground black pepper
• Pinch of kosher salt

Instructions

1. Place a rack in middle of oven and preheat to 325°F. Pulse gingersnaps in a food processor until very fine crumbs form (you should have about 2 cups). Add flour, raw sugar, and salt and pulse to combine. Add butter and pulse until mixture is the consistency of wet sand.
2. Transfer mixture to a 9" pie dish. Using a measuring cup, press firmly onto bottom and up sides of pie dish. Place pie dish on a rimmed baking sheet and bake crust, rotating halfway through, until dry and set, 20–25 minutes. Transfer pie dish to a wire rack and let crust cool.
3. DO AHEAD: Crust can be baked 1 day ahead. Store wrapped tightly at room temperature.
4. For filling, compote, and assembly: Place gelatin and 2 tablespoons milk in a small bowl and let stand until gelatin is softened, 5–10 minutes. Warm remaining 1/2 cup milk in a small saucepan over medium heat until steaming, about 3 minutes. Remove from heat, add gelatin mixture, and whisk until smooth. Whisk in yogurt, brown sugar, and lemon zest and pour into pie crust, smoothing top if needed; chill until set, at least 2 hours. Meanwhile, bring grapes, granulated sugar, lemon juice, pepper, and salt to a boil in a large skillet over medium-high heat, stirring to dissolve sugar. Reduce heat and simmer, stirring occasionally, until grapes burst and mixture is syrupy, 8–10 minutes. Let cool. Using a slotted spoon, spoon compote over pie slices just before serving. DO AHEAD: Pie and compote can be made 2 days ahead; cover separately and chill.
5. Place gelatin and 2 tablespoons milk in a small bowl and let stand until gelatin is softened, 5–10 minutes.
6. Warm remaining 1/2 cup milk in a small saucepan over medium heat until steaming, about 3 minutes. Remove from heat, add gelatin mixture, and whisk until smooth. Whisk in yogurt, brown sugar, and lemon zest and pour into pie crust, smoothing top if needed; chill until set, at least 2 hours.
7. Meanwhile, bring grapes, granulated sugar, lemon juice, pepper, and salt to a boil in a large skillet over medium-high heat, stirring to dissolve sugar. Reduce heat and simmer, stirring occasionally, until grapes burst and mixture is syrupy, 8–10 minutes. Let cool.
8. Using a slotted spoon, spoon compote over pie slices just before serving.
9. DO AHEAD: Pie and compote can be made 2 days ahead; cover separately and chill.