Crush 1 quart hulled strawberries or raspberries in a large bowl. Add ½ cup sugar and let stand 30 minutes.
Soak 2 teaspoons unflavored gelatin in 3 tablespoons cold water and let stand 5 minutes.
Add 3 tablespoons boiling water and stir to dissolve the gelatin, then stir into the berries.
Optional: add 1 tablespoon fresh lemon juice.
Chill the strawberry-gelatin mixture until it's the thickness of unbeaten egg whites.
Whip 1 cup cold heavy cream until firm peaks form.
Gently fold into the berry mixture.
Pour into a lightly oiled 1½ quart dish or mold.
Refrigerate for 8 hours if you plan to unmold the cream, or just scoop into serving dishes.