These are great when you want a taste of summer all year around! If you don't have frozen blackberries, substitute any variety of frozen berries or berry blend.
To make the crust, preheat the oven to 350 degrees.
Prepare a 9" x 13" baking pan with butter or cooking spray and set aside.
Combine the flour, sugar, and salt in a food processor for about 45 seconds.
Cut the butter into 1/2" cubes and process with the flour mixture for 30 seconds or until the butter is evenly distributed but the mixture is still crumbly.
Reserve 1 1/2 cups of the crust mixture to use as a topping.
Press the remaining crust mixture firmly into the bottom of the prepared pan.
Bake for about 25 minutes or until golden brown; allow to cool for at least 10 minutes before adding the filling.
For the filling, combine the eggs, sugar, sour cream and flour in a large bowl.
Fold in the blackberries.
Spoon the fruit filling evenly over the crust and sprinkle the reserved crust over the filling.
Bake for 45-55 minutes or until the top is lightly browned. Let cool for at least 1 hour before cutting into bars.