Wash the strawberries at least six hours before party time. Place one small, good berry (with leafy hulls attached) in each compartment of two standard-sized ice cube trays, then fill with water and freeze.
Remove the hulls from the remaining berries and place them in a food processor. Process for two minutes or until well pureed, then transfer into a large glass bowl.
Stir in the chilled pineapple juice, lemon juice, powdered sugar and blend well. Cover and refrigerate. Just before serving, mix the above mixture with champagne and serve in a champagne flute with a strawberry ice cube floating on top.