Brown Sugar Berry Shortcake

I am a huge fan of America's Test Kitchen recipes. I have their cookbook, get the magazine monthly, watch their weekly PBS show, and receive emails with new recipes. ATK recipes encourage home cooks to always cook from scratch. I have found their recipes to be delicious 100% of the time, as long as I follow them correctly. I just received this recipe in an email and it looks wonderful.

Fruit
6	cups mixed berries (see below for preparation instructions)
4 - 6	tablespoons packed light brown sugar
Shortcakes
2	cups all-purpose flour
3	tablespoons packed light brown sugar
1	tablespoon baking powder
1/2	teaspoon table salt
8	tablespoons unsalted butter (1 stick), cut into 1/2-inch pieces and chilled, plus 2 tablespoons unsalted butter, melted (for brushing on shortcakes)
1	large egg
1/2	cup sour cream
2	tablespoons granulated sugar
Brown-Sugar Cream Topping
1	cup heavy cream
1/4	cup sour cream
1/4	cup packed light brown sugar
How to Prepare Berries
	fresh strawberries --Hulled, halved, and sliced
	fresh raspberries --Whole
	fresh blackberries --Halved
	fresh blueberries --Whole
	currants --Whole

1. For the fruit: Crush 2 cups berries and brown sugar in large bowl with potato masher. Fold in remaining 4 cups berries and let sit at room temperature until sugar has dissolved and berries are juicy, about 30 minutes.

2. For the shortcakes: Adjust oven rack to upper-middle position and heat oven to 375 degrees. Line rimmed baking sheet with parchment paper. Pulse flour, brown sugar, baking powder, and salt in food processor until no lumps of sugar remain. Scatter chilled butter pieces over top and pulse until mixture resembles coarse meal, about 7 pulses. Transfer to large bowl.

3. Whisk egg and sour cream together in small bowl. Stir into flour mixture with rubber spatula until large clumps form. Using hands, knead lightly until dough comes together and no dry flecks of flour remain.

4. Using a large (#10) ice cream scoop, scoop 6 dough rounds onto baking sheet. Brush tops with melted butter and sprinkle with granulated sugar. Bake until golden brown, 25 to 30 minutes, rotating baking sheet halfway through baking time. Cool shortcakes on baking sheet 10 minutes. (Cooled shortcakes can be wrapped tightly in plastic wrap and kept on counter for up to 24 hours.)

5. For the topping: With electric mixer, beat heavy cream, sour cream, and brown sugar to stiff peaks. Split each shortcake in half using serrated knife and place bottoms on individual plates. Spoon portion of fruit over bottoms, top with whipped cream, and cap with shortcake tops. Serve.