Preparation Combine 1 cup blueberries and lemon juice in medium bowl; mash well. Sift powdered sugar into heavy medium nonstick skillet. Cook over medium heat until sugar begins to dissolve, stirring occasionally, about 5 minutes. Continue to cook until syrup turns deep golden brown, stirring often, about 5 minutes longer. Whisk in 1 cup cream and 1/4 cup water (mixture will bubble up). Reduce heat to medium-low, cover, and cook until most hard caramel bits dissolve, stirring occasionally, about 20 minutes. Remove from heat. Stir in mashed blueberries; strain into medium saucepan, pushing berries through. (Can be made 3 days ahead. Cover; chill.) Rewarm sauce over low heat. Beat 3/4 cup cream in medium bowl to soft peaks. Place 1 scoop each of vanilla ice cream, raspberry sorbet, and strawberry ice cream in each of 6 sundae dishes. Spoon warm sauce over. Top with remaining blueberries, whipped cream, and pecans.
Preparation Combine 1 cup blueberries and lemon juice in medium bowl; mash well. Sift powdered sugar into heavy medium nonstick skillet. Cook over medium heat until sugar begins to dissolve, stirring occasionally, about 5 minutes. Continue to cook until syrup turns deep golden brown, stirring often, about 5 minutes longer. Whisk in 1 cup cream and 1/4 cup water (mixture will bubble up). Reduce heat to medium-low, cover, and cook until most hard caramel bits dissolve, stirring occasionally, about 20 minutes. Remove from heat. Stir in mashed blueberries; strain into medium saucepan, pushing berries through. (Can be made 3 days ahead. Cover; chill.) Rewarm sauce over low heat. Beat 3/4 cup cream in medium bowl to soft peaks. Place 1 scoop each of vanilla ice cream, raspberry sorbet, and strawberry ice cream in each of 6 sundae dishes. Spoon warm sauce over. Top with remaining blueberries, whipped cream, and pecans.