Combine dried peaches and 3/4 cup peach nectar in a medium saucepan. Bring to a boil; cover, reduce heat, and simmer 20 minutes. Remove from heat, and let stand 10 minutes. Process cooled peaches and cooking liquid in a blender or food processor until smooth.
Combine mascarpone cheese and 1 cup whipping cream in a medium bowl; beat at medium speed with an electric mixer until smooth and thickened. Add 1/4 cup powdered sugar and peach puree, mixing well. Set aside.
Combine 3/4 cup granulated sugar, water, cream of tartar, and pecans in a heavy saucepan. Bring mixture to a boil; boil 5 minutes, without stirring (mixture will be the color of molasses). Immediately pour pecan mixture onto a lightly greased baking sheet; cool 20 minutes. Break cooled pralines into pieces; process in batches in food processor until mixture resembles coarse brown sugar. Set aside, reserving 1/4 cup praline mixture for garnish.
Line bottom and sides of a lightly greased 9-inch springform pan with 1 1/2 packages ladyfingers, cut side in, forming a double layer on bottom of pan. Combine 1/2 cup peach nectar and peach schnapps in a small bowl; drizzle half of peach schnapps mixture over ladyfingers in bottom of pan. Sprinkle half of praline mixture over ladyfingers. Spoon mascarpone cheese mixture over praline layer; spread evenly. Sprinkle with remaining half of praline mixture. Top with remaining 1/2 package ladyfingers; drizzle with remaining peach schnapps mixture. Cover and chill 8 hours or overnight.
Beat 1 cup whipping cream and 2 tablespoons powdered sugar at high speed with an electric mixer until soft peaks form. Remove sides of springform pan; spread top evenly with sweetened whipped cream. Top with fresh peach slices, if desired, and reserved 1/4 cup praline mixture. Store in refrigerator.