3 cups all-purpose flour
1/2 cup (packed) golden brown sugar
3-3/4 teaspoons baking powder
2-1/4 teaspoons ground cardamom
3/4 teaspoon baking soda
3/4 teaspoon salt
3/4 cup (1-1/2 sticks) chilled unsalted butter, cut into 1-inch pieces
3 large eggs
About 1/2 cup chilled buttermilk
1-1/2 teaspoons vanilla extract
1-1/2 tablespoons melted butter
Sugar for sprinkling
8 medium, ripe peaches (about 2-1/2 pounds), peeled, pitted, sliced
4 cups fresh blueberries
3/4 cup sugar
2 teaspoons vanilla extract
1 teaspoon cardamom
3/4 cup sour cream
1 cup heavy whipping cream
Preheat oven to 425 degrees. Line baking sheet with parchment paper.
Combine flour, brown sugar, baking powder, cardamom, baking soda and salt in food processor. Pulse to combine. Add butter and pulse until mixture resembles coarse meal. Transfer to large bowl.
Beat eggs in glass 4-cup measuring cup. Add enough buttermilk to equal 9 ounces (1 cup plus 2 tablespoons). Add vanilla. Using fork, mix buttermilk mixture into dry ingredients just until dough binds together.
Gently push dough together on dry, floured work surface. Divide dough into 3 equal portions. Form 1 dough piece into ball and flatten to 1-inch-thick round. Cut into 4 wedges. Transfer to prepared baking sheet, spacing evenly. Repeat forming and cutting with remaining 2 dough pieces.
Brush with melted butter; sprinkle with sugar. Bake until just firm to touch and beginning to brown, about 15 minutes. Transfer to cooling rack.
Combine peaches, blueberries, sugar, vanilla and cardamom in large bowl. Mix to combine. Let stand until juices form, stirring occasionally, at least 20 minutes. In separate bowl, place sour cream. Gradually mix in whipping cream.
Assemble: Split warm shortcakes in half. Place bottoms in shallow bowls. Spoon fruit mixture over. Top each with large spoonful of sour cream mixture. Cover with top half of shortcake and another spoonful of sour cream mixture. Serve immediately.