CRUST

1. In medium bowl, whisk flour and sugar. Using a pastry blender or long-tined fork cut in chilled butter until the mixture becomes crumbly about the size of small peas. Add buttermilk 1 tablespoon at a time and combine dough until the mixture leaves the sides of the bowl.
2. Over a floured surface, form pastry dough into a ball, divide in half and flatten each round into a disk shape. Cover each separately with plastic wrap and cool in fridge for 30 minutes.

FILLING

1. Meanwhile, heat oven to 425 degrees F. In a large bowl using a rubber spatula, gently toss all berries with 2/3 cup of sugar and cornstarch until coated; set aside.
2. Using a floured rolling pin over a floured surface, roll out dough into a circle about 12 inches in diameter. Loosely roll dough around the rolling pin to transfer to a 9-inch pie plate. Trim overhang to about 1/2 inch beyond lip of plate. Crimp dough as desired.
3. Spoon filling into plate, leave any berry juice behind; set filled plate aside.
4. Roll out second half of pie dough, using a pleated pie cutter, cut out 6 12-inch long lattice strips about 1/2-inch wide. Reroll dough if needed and cut 4 12-inch long straight edge strips about 1/4-inch wide.

ASSEMBLY

1. Lay 3 pleated lattice strips about an inch apart and parallel to each other over the filling. Tip: keep the longest strips in the center. Turn plate 45 degrees and lay remaining pleated strips perpendicular to another. Gently pull back every other bottom strip to lay the top strip on top to complete the lattice design. Lay the 4 straight-edge strips across the center.
2. Brush each strip with heavy cream or milk and generously sprinkle coarse sugar.
3. Bake uncovered for 20 minutes on center rack. Loosely cover pie with a sheet of foil and continue to bake for another 20 minutes until berries begin to bubble and the crust is golden brown.
4. Allow pie to cool in plate over a wire rack till room temperature before serving. ENJOY!