We had a very special picnic with a very special friend tonight, for whom I made a very special pie. His favorite berries--strawberry and blueberry--minus any sugar, which he can't have. I simply heated a jar of sugarless strawberry jam (the kind that is sweetened only with fruit juices) until it was liquid, whisked in 4 teaspoons of cornstarch, and tossed it with 2 pounds of strawberries and a sprinkling of blueberries. For the crust I made the Pie Dough Cockaigne recipe from The Joy of Cooking, minus the 2 teaspoons of sugar that it calls for. I par-baked the bottom crust for 15 minutes, then dumped in the berries, wove the lattice top, and baked it for another 20 minutes. It was absolutely perfect. And so was our picnic.