Rub pears with lemon juice to prevent browning.
Place steamer rack in large saucepan or Dutch oven.
Add enough water to cover bottom of pan (water should not touch rack).
Place pear halves, cut sides down, on steamer rack; cover.
Heat over medium heat until water boils.
Reduce heat to low; steam pears 4 to 5 minutes until tender when pierced with knife tip.
Cool to room temperature; refrigerate until cold.
Meanwhile, place raspberries in blender or food processor; blend until smooth.
Press through sieve to remove seeds.
Stir sugar into yogurt.
Place yogurt in pastry bag fitted with fine tip or in clean plastic squeeze-type mustard or ketchup botde.
Pour about 1/4 cup raspberry puree onto each of 4 dessert plates.
Pipe yogurt in spiral design on sauce.
Draw knife from center of plate to edge, spoke-fashion, to create web design.
Place each chilled pear half, cut side down, in center of sauce on individual plates.
Garnish with orange peel and mint leaves, if desired.