Position rack in center of oven and preheat to 350°F. Mix applejack brandy, dried currants, fresh lemon juice and vanilla extract in large bowl. Let mixture stand 15 minutes.
Cook 3 tablespoons unsalted butter in heavy large skillet over medium heat until pale golden, about 3 minutes. Add apple wedges, ground cinnamon and ground nutmeg. Sauté until apple wedges are crisp-tender, about 12 minutes. Add apple mixture, pear wedges and 2 tablespoons cornstarch to currant mixture; toss to coat.
Mix golden brown sugar, corn syrup, whipping cream and remaining 2 tablespoons unsalted butter in heavy small saucepan. Boil over medium-high heat until slightly thickened, stirring until sugar dissolves, about 5 minutes. Stir in chopped walnuts. Add to fruit mixture. Toss to coat.
Transfer warm filling to prepared crust. Bake 30 minutes. Tent pie with foil. Bake pie until apples and pears are tender and liquid bubbles thickly, about 45 minutes longer.
Cool pie on rack. Serve warm or at room temperature with ice cream.
