Process 1 quart of strawberries, 1/2 a pint of blueberries, and 1/2 cup of sugar in a food processor until mixture is completely smooth, about 1 minute.

Strain berry puree through a fine-mesh strainer into a 4-cup liquid measuring cup (you should have 2 and 1/2 cups puree; reserve any excess for another use).

Transfer half a cup of puree to a small bowl and sprinkle kolatin over the top; stir until gelatin is incorporated and let stand for at least 5 minutes.

Heat remaining 2 cups of puree in a small saucepan over medium heat until it begins to bubble, 4 to 6 minutes. Remove pan from heat and stir in kolatin/fruit mixture until dissolved. Transfer puree mixture to a medium bowl, cover with plastic wrap, and refrigerate until cold, about 2 hours.

Meanwhile, chop remaining 1 quart of strawberries into rough 1/4-inch pieces. Toss chopped strawberries, remaining 1/2 pint of blueberries, and 2 tablespoons of sugar together in a medium bowl. Set aside for 1 hour.

Place heavy cream, sour cream, vanilla, and remaining 2 tablespoons of sugar in the chilled bowl of an electric stand mixer. Beat on low speed until bubbles form, about 30 seconds.

Increase speed to medium and continue beating for another 30 seconds.

Increase speed to high; continue beating until mixture has nearly doubled in volume and holds stiff peaks, about 30 seconds. Transfer 1/3 cup whipped-cream mixture to a small bowl and set aside.

Remove thickened berry puree from refrigerator and whisk until smooth.

With mixer running at medium speed, slowly add two-thirds of puree to whipped cream mixture; mix until incorporated, about 15 seconds.

Using a spatula, gently fold in remaining thickened puree, leaving streaks of puree in whipped cream mixture.

Transfer uncooked berries to a fine-mesh strainer; shake gently to remove any excess juice.

Divide two-thirds of berries evenly among 6 tall parfait or sundae glasses.

Divide creamy berry mixture evenly among glasses, followed by remaining uncooked berries.

Top each glass with reserved plain whipped-cream mixture.

Sprinkle with crushed crackers.

Serve immediately.