When I saw the name of this recipe, I knew I had to try it. When I saw this it made me think of the 3 mountains in central Oregon called the three sisters. Plus, this pie has my favorite berries in it, so I knew it would be good.
Combine the flour and salt in a bowl. Cut in the shortening until the mixture is crumbly. Add the water 1 tsp at a time, tossing with a fork until the pastry holds together. Shape into two balls, one slightly larger than the other; flatten into disks. Gently toss the strawberries, blueberries, and raspberries, with mixture of cornstarch, and apple juice in a bowl. Let stand for 15 minutes. Gently mix in the sugar and cinnamon.
Preheat the oven to 450 degrees. On a lightly flour surface, roll the larger pastry disk into a 12 inch circle. Fit it into a 9 inch pie pan leaving a 1 inch overhang. Spoon in the filling and dot with the butter. Roll the remaining disk into a 11 inch circle. Cut into 1/2 inch strips. Twist each strip. Arrange the strips in a lattice pattern on top of the filling. Trim the ends and flute the edge. Place on a cookie sheet and bake 15 minutes. Reduce the temperature to 350 degrees and bake 55 more minutes or until the filling is bubbly and the crust is golden brown.