Combine brandy and cherries in a 1- to 1 1/2-quart pan; cover and set over low heat just until hot, about 3 minutes. Remove from heat and let stand until cherries are slightly softened, at least 5 minutes.
Meanwhile, in a large bowl, mix granulated sugar, cornstarch, coriander, ginger, and nutmeg. Stir in pears and the cherry mixture.
On a lightly floured board, roll pastry into a 12-inch round. Ease, without stretching, into a 9-inch pie pan. Fold excess pastry around edge under itself and flute edge. Pour fruit mixture into pastry.
In a food processor or bowl, mix flour and brown sugar. Whirl or rub in butter with your fingers until mixture forms coarse crumbs. Add nuts and whirl or stir just until combined. Squeeze handfuls of the streusel mixture until it sticks together, then coarsely crumble into 1/2-inch chunks over fruit.
Set pan in a foil-lined rimmed baking pan and bake on the bottom rack of a 375° regular or convection oven until juices bubble around edges, 1 to 1 1/4 hours. If pie browns too quickly (check after 30 minutes), drape dark portions loosely with foil. Let cool on a rack for at least 1 1/2 hours.