For bombe: Rinse 6 cup ring mold and place in freezer about 15 minutes.
Spoon ice cream into mold.
Using back of spoon dipped in hot water, spread ice cream evenly to coat interior of mold.
Freeze about 1 hour, or overnight.
Combine sugar and water in heavy small saucepan.
Place over medium heat and cook without stirring until sugar is dissolved and liquid is clear.
Increase heato high and boil until syrup reaches 242°F on candy thermometer, washing down any crystals forming on sides of pan with pastry brush dipped in cold water.
Meanwhile, beat yolks with electric mixer at medium speed until thick and lemon colored.
Increase speed to high and add syrup in thin, steady stream, beating constantly until mixture cools to room temperature.
Mix in puree, brandy and vanilla.
Chill thoroughly.
Fold whipping cream into mixture, blending completely.
Pour into mold.
Tap mold lightly on counter to settle filling, cover with plastic wrap and freeze.
For sauce: Several hours before serving, add lemon juice to medium bowl.
Slice peaches into thin crescents and halve each crescent.
Toss pieces in lemon juice to prevent darkening.
Set aside.
Combine raspberries, liqueur, vanilla and sugar in processor or blender and puree.
Add to peaches and blend well.
Cover and chill several hours.
One hour before serving, wrap mold in hot towels or dip briefly into hot water and unmold bombe onto large round platter.
Return to freezer.