In a small bowl, combine the strawberries, blueberries and 2 tablespoons sugar; set aside.
In a large bowl, combine the flour, 1/4 cup sugar, baking soda and salt. Cut in butter until mixture resembles coarse crumbs. Combine milk and sour cream; stir into crumb mixture just until moistened.
Spread batter into a greased 9-in. pie plate (batter will be thick). Sprinkle with remaining sugar. Bake at 350° for 16-20 minutes or until a toothpick comes out clean. Cool on a wire rack for 10 minutes; cut into six wedges.
To assemble, cut each wedge in half; place bottoms on dessert plates. Top each with berry mixture. Replace wedge tops. Garnish with whipped cream if desired.