Preheat oven to 375�. Coarsely chop nuts with brown sugar, flour and salt in processor. Add butter, process until nuts are finely chopped. Press half of mixture over bottom of 9� springform pan. Press remaining half of mixture over bottom of 9� cake pan. Bake until crusts are golden, about 20 minutes. Transfer to racks; cook completely. Break crust in pans into crumbs.
Place 1 tbs water in small bowl. Sprinkle gelatin over; let stand until gelatin softens, about 10 minutes. Whisk yolks, sugar, kirsch and 3 tbs water in medium metal bowl until blended. Set bowl over saucepan of simmering water; whisk constantly until mixture registers 160� on candy thermometer, about 4 minutes. Remove bowl from over water. Add gelatin, then white chocolate and whisk until gelatin dissolves and chocolate melts. Let stand until mixture is cool but not set, whisking occasionally, about 10 minutes. Beat cream in large bowl until soft peaks form. Fold yolk mixture into cream.
Spread one third of mousse over crust in spring form pan. Sprinkle half of chopped peaches over. Sprinkle half of crumbs over peaches. Drop one third of mousse by tablespoons over peaches, spacing evenly. Spread mousse carefully over, covering crumbs. Sprinkle with remaining chopped peaches and crumbs. Carefully spread remaining mousse evenly over. Cover and freeze over night. (Can be made 3 days ahead. Keep frozen.) Mix peach slices and powdered sugar in medium bowl. Let stand 15 minutes. Using knife, cut around pan sides to loosen torte. Release pan sides; transfer torte to platter. Arrange peaches in concentric circles atop torte. Let stand at room temperature 30 minutes and serve.