Peach and Pistachio Praline Semifreddo

Line baking sheet with foil; spray with nonstick spray. Combine sugar, 1/2 cup water, and corn syrup in heavy medium saucepan; stir over medium heat until sugar dissolves. Increase heat; boil until syrup is deep amber, occasionally swirling pan and brushing down sides with wet pastry brush, about 10 minutes. Remove from heat. Add nuts; stir until coated. Immediately pour mixture out onto prepared sheet of foil and spread so that nuts are in single layer. Cool completely. Break off 1/4 of nut praline and coarsely chop, then transfer pieces to processor. Process until praline resembles fine powder; transfer to airtight container. Chop remaining praline into 1/4-inch pieces; transfer to another airtight container. DO AHEAD: Can be made 1 week ahead. Store both airtight containers at room temperature.