Adapted from Patricia Poole of Kincaid Farms in Redlands. She says, "The idea of using strawberries is that they are less expensive than boysenberries. Try not to eat the whole pie if anyone is watching."
1 pint boysenberries, divided, more as desired for assembly
1 cup water
1/3 to 3/4 cup sugar
3 tablespoons cornstarch
Pinch of salt
1 pint strawberries (sliced if they're large), more as desired for assembly
1 prepared (9-inch) pie shell
Whipped cream, optional
1. In a medium saucepan, crush 1 cup of the boysenberries with a fork. Add the water and cook over low heat just enough to soften the berries, about 2 minutes. Sieve the boysenberries through a food mill or a fine strainer to extract the seeds, collecting the juice in a bowl and then returning it to the saucepan.
2. In a bowl, combine the sugar (the amount of sugar will affect the sweetness of the pie), cornstarch and a pinch of salt. Slowly pour the mixture into the boysenberry juice, stirring to prevent lumps. Cook over medium-high heat, stirring constantly, just until the puree thickens, about 3 minutes.
3. Place a layer of strawberries in the prepared pie shell. Scatter half the remaining boysenberries on top of the strawberries, and top with just enough sauce to cover the first layer. Repeat for the second layer, adding remaining strawberries, boysenberries and sauce.
4. Chill in the refrigerator until set, at least 30 minutes. Serve with whipped cream.