Preheat oven to 425F. In medium bowl, combine flour and 1/4 cu sugar; add 1 1/3 cu heavy cream. With fork, stir until soft dough begins to form a ball. Turn out onto lightly floured surface; knead gently 4 times. Pat into 10x3 inch strip; cut crosswise into 6 lengths. Place on heavy baking sheet. Bake 15 minutes or until light brown. Cool on wire rack.
In medium saucepan, place 1 cup strawberries; with potato masher or fork, mash. Reserve 2 T sugar; add remainder to mashed strawberries. Heat to boiling; boil 1 minute. Pour into medium bowl; chill thoroughly.
Slice remaining strawberries; add to cooled mashed berries. Add blueberries; mix.
In small bowl of electric mixer, at high speed, whip remaining cream with reserved sugar until soft peaks form.
To serve: Split shortcakes horizontally, fill with berries and whipped cream. Replace tops.