Berry-rhubarb fans will love this gelato.
Place rhubarb and 3 tablespoons water in a medium saucepan. Cook over medium heat, stirring often, until very soft and most of the liquid has evaporated, about 45 minutes. Remove from heat and puree rhubarb with 1 1/2 pints of the raspberries. Strain puree and set aside to cool.
Meanwhile, combine milk, cream, andcorn syrup in a small saucepan. Heat to barely boiling. Combine dry milk, sugar, and gelatin and whisk in. Bring back to barely boiling to dissolve gelatin, and remove pan from heat. Pass mixture through a strainer into a medium bowl set over an ice bath to chill. Stir in fruit puree, then freeze in an ice-cream maker according to manufacturer's instructions. Add remaining raspberries and mix in machine until combined, about 30 seconds. Store in a plastic container.
For best flavor, soften it slightly in the refrigerator before serving.
Strawberry Variation: Substitute 2 1/2 pints strawberries, hulled, for the rhubarb and raspberries.
Apricot Variation: Substitute 2 1/2 pounds (10 to 12) ripe apricots, pitted, for the rhubarb and raspberries.