01 -
Drain blueberries over a colander into a large measuring cup, then add water to the collected syrup until it totals 4 cups of liquid.
02 -
Pour the liquid into a medium saucepan and heat to a simmer over medium heat. Remove from heat, add the gelatin mix, and stir continuously until smooth with no granules remaining, about 1 to 2 minutes. Transfer to a medium mixing bowl.
03 -
Prepare an ice bath in a large bowl with ice and water. Lower the bowl containing the gelatin mixture into the ice bath so water reaches halfway up the sides. Stir every few minutes until the mixture is slightly wobbly but not firm, approximately 30 minutes, or when temperature reaches 45 to 55°F.
04 -
Remove the gelatin bowl from the ice bath. Add sour cream and blueberries, stirring until fully combined with minor streaks of white acceptable.
05 -
Pour mixture into a 10 ½-cup gelatin mold or bundt pan. Tap gently on countertop to settle evenly, cover with plastic wrap, and refrigerate until fully set, at least 8 hours or overnight.
06 -
Fill a large bowl halfway with warm (not boiling) water. Dip mold into water for about 10 seconds, remove, place serving plate on top, and invert carefully. Repeat dipping and inverting if necessary until dessert releases easily.
07 -
Cut the gelatin mold into slices using a cake server and transfer to plates to serve immediately.