Macerate 4 cups fresh or frozen blackberries with 1 cup sugar; mash and strain. This will yield about 3 cups of syrup. Sift together 1 cup sugar, 1 tablespoon cornstarch, and a generous dash of salt. Drizzle this mix into a quart of warm half-and-half, add 2 eggs well beaten and 1 teaspoon pure vanilla extract. Simmer until thickened, about 2 minutes, maybe more. Remove from heat, add 2 cups whole cream, another teaspoon of vanilla, and the blackberry syrup. Whisk until smooth. Refrigerate before processing in the ice cream freezer. This recipe works well with any berry or stone fruit.