For the Crust

1. In a food processor, pulse together flour, butter, and sugar until there are pea-sized bits of flour coated butter. Pour into a mixing bowl, and add sour cream, stirring together.  Use clean hands to bring the dough together.  It will be a bit crumbly but will come together as it chills and rests.
2. Wrap the dough with plastic wrap and shape into a disk.  Refrigerate for at least 4 hours, or freeze until ready to use.
3. When ready to make the pie, roll the dough out into a circle so that it is 1 inch larger than the outside of the pie plate.  I like to roll the dough between two pieces of plastic wrap so it doesn’t stick to the counter or rolling pin, and I don’t need to add additional flour.  Remove the top piece of plastic wrap, and roll the dough loosely around the rolling pin to transfer it to the pie dish.  Without stretching the dough, allow it to fall into the bottom of the pie dish.  Then remove the other piece of plastic wrap.
4. Roll the excess edges of the pie dough down and shape as desired.  Freeze the unbaked pie crust while the filling and topping are prepped.

For the Filling

1. Preheat the oven to 400 degrees. In a large bowl, mix quartered strawberries, raspberries, sugar, and flour until evenly coated.
2. Pour the berry filling into the chilled pie crust.

For the Crumble Topping

1. In a large bowl, mix oats, flour, sugar, and salt.  Add cubes of butter and work into the oat mixture with a fork, pastry cutter, or clean hands.  The topping will just hold together with some loose crumbs. Pour the topping evenly over the filled pie.
2. Place the pie onto a baking sheet to catch drips, and bake for 1 hour to 1 hour and 20 minutes.  The juice from the berries should be thick and bubbly, and the topping golden brown.  Use a pie shield or piece of tin foil to cover the edges and top if they become too brown.
3. Allow the pie to cool before slicing and serving.  Serve with ice cream or whipped cream.