I made this pie more than once, adjusting the fruit amounts according to what I had on hand. You can do the same. Below, however, is the recipe with the ratios I liked best.
THE RECIPE:
2 c. blueberries
2 c. strawberries, halved
1 c. boysenberries
1/3 c. flour
2/3 to 3/4 c. sugar, depending on tartness of berries
3/4 tsp. cinnamon
1/2 Tbsp. lemon juice
1/2 to 3/4 c. semi-sweet chocolate chips*
Gently mix berries with flour, sugar, cinnamon and lemon juice. Allow to sit while making crust dough. Stir in chocolate chips, then pour filling into bottom crust. Make lattice-style crust on top or whatever design your heart desires -- something that allows ventilation. Brush top crust with milk and sprinkle with sugar. Bake at 375 degrees for 50 minutes. Line outer edges with foil if needed to prevent burning. I didn't need to do that. Let cool completely on wire rack before eating.
Crust recipe:
2 1/4 c. flour
3/4 tsp. salt
1/3 c. shortening
1/3 c. cold butter
8 to 10 Tbsp. cold water
Stir together flour and salt, then cut in shortening and butter with pastry blender until you have pea-sized crumbs. Mix in water until dough forms. Roll out dough on lightly floured surface. You'll need two 12-inch circles for a 9-inch pie pan.
*I made it both ways. I liked it with more chocolate, and my husband liked it with less -- he loves baked fruit, though, so he wanted the fruit to shine with just a hint of chocolate. I wanted chocolate in every bite.