Berry Fool

1. Process half of strawberries, half of raspberries, and 1⁄2 cup sugar in food processor until mixture is completely smooth, about 1 minute. Strain berry puree through fine-mesh strainer into large liquid measuring cup (you should have about 2-1⁄2 cups puree; reserve excess for another use). Transfer 1⁄2 cup of puree to small bowl and sprinkle gelatin over top; let stand at least 5 minutes to soften and stir. Heat remaining 2 cups puree in small saucepan over medium heat until it begins to bubble, 4 to 6 minutes. Off heat, stir in gelatin mixture until dissolved. Transfer to medium bowl, cover with plastic wrap, and refrigerate until well chilled, about 2 hours.
2. Meanwhile, chop remaining strawberries into rough 1⁄4-inch pieces. Toss strawberries, remaining raspberries, and 2 tablespoons sugar together in medium bowl. Set aside for 1 hour.
3. Using stand mixer fitted with whisk, whip cream, sour cream, vanilla, and remaining 2 tablespoons sugar on low speed until bubbles form, about 30 seconds. Increase speed to medium and whip until whisk leaves trail, about 30 seconds. Increase speed to high; whip until mixture has nearly doubled in volume and holds stiff peaks, about 30 seconds. Transfer 1⁄3 cup of whipped cream mixture to small bowl; set aside.
4. Remove berry puree from refrigerator and whisk until smooth. With mixer on medium speed, slowly add two-thirds of puree to whipped cream mixture; mix until incorporated, about 15 seconds. Using spatula, gently fold in remaining puree, leaving streaks of puree.
5. Transfer uncooked berries to fine-mesh strainer; shake gently to remove any excess juice. Divide two-thirds of berries evenly among six 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 and garnish with mint sprigs, if using. Serve immediately.

Blueberries or blackberries can be substituted for the raspberries in this recipe. You may also substitute frozen fruit for fresh, but it will slightly compromise the texture. If using frozen fruit, reduce the amount of sugar in the puree by 1 tablespoon. The thickened fruit puree can be made up to 4 hours in advance; just make sure to whisk it well in step 4 to break up any clumps before combining it with the whipped cream. For the best results, chill your beater and bowl before whipping the cream.