1. Lightly grease a 9x13" glass baking dish and set aside.
2. Whisk sugar and gelatin in a medium saucepan until completely blended. Gradually stir in 2 cups sparkling wine, about one-third at a time, making sure each portion is fully incorporated before adding the next; let sit 5 minutes to soften gelatin.
3. Place over medium-low heat and cook, stirring constantly, until gelatin is completely dissolved and mixture is warm, 8 to 10 minutes, reducing heat as needed to keep mixture from coming to a boil. Scrape into a large bowl, then whisk in 2 more cups sparkling wine and let sit until no longer foamy.
4. Whisk in remaining 2 cups sparkling wine along with the lemon juice, then let sit until foam mostly subsides. Skim off any remaining foam and pour mixture into prepared pan.
5. Cover with plastic wrap and refrigerate until firm and fully set, 8 to 12 hours, before cutting into 1 1/2" squares. Serve cold.
Source: Hannaford fresh Magazine, December 2021