This is a delicious treat made with fresh blackberries! Very simple to prepare for snack or dessert.
Preheat oven to 350 degrees.
Combine flour and brown sugar, cut in butter with a pastry blender until mixture resembles coarse meal.
Press 1 1/3 cups of mixture in bottom of an ungreased 8x8 inch square pan.
Combine remaining crumb mixture, sour cream, and next five ingredients.
Blend well.
Stir in blackberries.
Spoon over crust, spreading evenly.
Bake at 350 degrees for 35 minutes.
Let cool; cut into bars.
Sprinkle with powdered sugar.