Special equipment: 6 wine glasses; a pastry bag
Put a strainer over a glass bowl. Put the lemon zest and juice and the granulated sugar in a heavy bottom, non-reactive saucepan over high heat and stir until the sugar dissolves, 3 to 5 minutes. Turn the heat to low, making sure the mixture is below a simmer, and whisk in the butter and eggs. Cook, stirring regularly and taking care to keep it below a simmer, until thickened, 9 to 10 minutes. Strain into the glass bowl, press some plastic wrap on the surface and cool.
Meanwhile, combine the berries, 1/4 cup confectioners' sugar and the sparkling wine in a large bowl. Cover and refrigerate while the curd cools.
Whisk the cream and the remaining 1/4 cup confectioners' sugar together in a large bowl until thick and creamy and just under soft peaks. Fold the cream into the cooled lemon mixture. Transfer the chiffon to a pastry bag; snip off the tip of the bag.
Pipe some of the lemon chiffon into the bottoms of the wine glasses, then spoon in some berries with their juices; repeat, finishing with just a few berries on the tops. Serve immediately.