Place a rack in middle of oven and preheat to 325°F. Toast fennel seeds in a small dry skillet over medium heat, stirring often, until fragrant, about 2 minutes. Transfer to a small plate; let cool, then finely chop. Pulse cookies in a food processor until very fine crumbs form (you should have about 2 cups). Add fennel seeds, flour, raw sugar, curry powder, and salt and pulse to combine. Add butter and pulse until mixture is the consistency of wet sand. 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, 2025 minutes. Transfer pie dish to a wire rack and let crust cool. DO AHEAD: Crust can be baked 1 day ahead. Store wrapped tightly at room temperature. Place gelatin and 2 tablespoons milk in a small bowl; let stand until gelatin is softened, 510 minutes. Place granulated sugar in a medium saucepan; scrape in seeds from vanilla bean and add pod. Cook over medium heat, stirring, until sugar is melted, then cook, stirring occasionally, until mixture turns amber in color, about 3 minutes. Remove from heat and slowly add cream (mixture will bubble vigorously), stirring until smooth. Return to heat and add 1/2 cup brown sugar and remaining milk. Cook, stirring, until sugar is dissolved and caramel mixture begins to steam, about 2 minutes. Remove from heat, add baking soda, and whisk until bubbles subside; remove pod and discard. Whisk egg yolks, cornstarch, and remaining 1/4 cup brown sugar in a medium bowl. Gradually whisk in half of warm caramel mixture. Pour egg-yolk mixture into caramel mixture in saucepan and bring to a boil over medium heat, whisking constantly; reduce heat to low and cook, whisking constantly, until thickened, 2 minutes. Remove from heat and add gelatin mixture, butter, molasses, and salt, whisking until butter is melted and mixture is smooth. Transfer filling to a large bowl and chill, stirring occasionally, until slightly cooled and thickened, about 1 hour. (Stirring and cooling pudding before chilling in crust will give it a luscious, creamy texture.) Pour butterscotch filling into crust, smoothing top if needed. Chill until set, at least 2 hours. Just before serving, spoon whipped cream over pie and top with cashews. DO AHEAD: Pie can be made (without whipped cream) 2 days ahead. Cover and keep chilled.