Sunday, July 18, 2010

Blackberry-Brown Sugar Cake

Adapted from Gourmet, September 2006
Serves 10
Blackberry-Brown Sugar Cake
For the blackberry syrup:
1 # blackberries (about 3 1/2 cups)
1/2 cup granulated sugar
1 tsp fresh lemon juice
For the cake:
2 oz walnuts (2/3 cups)
1 cup granulated sugar, divided
2 sticks unsalted butter, softened, plus more for greasing the cake pans
2 cups all-purpose flour
1 1/4 tsp baking soda
1 tsp salt
1 cup buttermilk, well shaken
1 tsp finely grated orange zest
2 Tbl fresh orange juice
1 1/2 tsp vanilla
1 cup light brown sugar, packed
2 large eggs
For the buttercream frosting:
3 large egg whites, room temperature
1/4 tsp salt
3/4 cup dark brown sugar, packed
1/3 cup water
3 sticks unsalted butter, cut into pieces and softened
1 1/2 tsp vanilla
For assembling the cake:
1 # blackberries (about 3 1/2 cups)
Make the blackberry syrup:
Combine the blackberries and sugar in a medium-sized saucepot and mash using a potato masher or fork.  Cook over medium-high heat, stirring occasionally, until slightly thickened, about 10-12 minutes.  Stir in the lemon juice.  Strain through a mesh sieve, pushing down on the solids to extract as much juice as possible.  Discard the seeds.  Chill the syrup in the refrigerator, until softly set, about 15 minutes.  This can be made at least a day ahead and kept refrigerated in an air-tight container.  Bring to room temperature before using. 
Make the cake
Preheat the oven to 350ᵒF and arrange the racks in the upper and lower thirds of the oven.
Using a food processor, pulse the walnuts with 1/2 cup sugar until finely ground.  Generously butter 3 8-inch round cake pans.  (It’s okay to use 9-inch pans too, but your cake won’t be as tall.)  Divide the walnut-sugar mixture between the three pans (about 1/3 cup per pan).  Tilt the pans to coat the bottoms and sides with the walnut-sugar mixture, letting the excess remain over the bottom of the pans.
In a medium-sized mixing bowl, combine the flour, baking soda and salt.  Whisk to thoroughly combine.  In a separate small mixing bowl, stir together the buttermilk, orange zest, orange juice and vanilla.
Using an electric stand mixer with the paddle attachment, beat together the butter (2 sticks), light brown sugar, and the remaining 1/2 cup of granulated sugar, on medium-high speed, until pale and fluffy, about 5 minutes.  Add the eggs, one at a time and beating well after each addition.  Reduce the speed to low and add the flour and the buttermilk mixtures alternatively in batches, beginning and ending with the flour mixture.  Mix just until the batter is smooth.  Divide the batter evenly among the three cake pans.
Bake, rotating the position of the pans about half-way through baking, until the edges begin to pull away from the sides of the pan and a wooden skewer inserted into the center of the cakes comes out clean, about 30 minutes.  Cool the cakes in the pans, placed on wire racks, for 15 minutes.  Then run a thin knife around the edge of each pan.  Invert racks over the pans, then flip the cakes onto the racks.  Cool completely to room temperature, about 1 hour.  The cake layers can be baked up to 2 days ahead and kept at room temperature, wrapped in plastic.
Make the buttercream frosting:
Place the egg whites and salt into the bowl of an electric stand mixer, fitted with the whisk. 
Combine the the dark brown sugar and water in a small saucepot.  Bring to a boil over medium-high heat, stirring until the sugar is dissolved.  When the sugar syrup begins to boil, start beating the egg whites at medium-high speed until they just hold soft peaks (When you stick a spoon into the cream and lift it out, a point will form then droop down after a second or two). (Do not beat them again until the sugar syrup is ready.)
Meanwhile, continue boiling the sugar syrup until it reaches 238-242ᵒF.  Immediately remove it from the heat and with the mixer at high speed, slowly pour the hot syrup into the egg whites (avoid the beaters), beating constantly.
Continue to beat the meringue, scraping down the bowl with a rubber spatula once or twice, until the meringue is cool to the touch, about 10 minutes.  (It is very important the the meringue is cool before continuing, or the butter will melt!!!) 
With the mixer at medium speed, gradually add the butter to the meringue, 1 piece at a time, and beating well after each addition until it is well incorporated.  Continue beating until the buttercream is smooth.  (The mixture may look curdled and thin before all the butter is added.  But don’t worry – it will come back together as the beating continues.)  Add the vanilla and beat 1 minute more.  The buttercream can be made ahead and chilled in an air-tight container for up to 1 week.  Bring to room temperature and beat with an electric mixer until smooth before using.
Assemble the cake
Put 1 cake layer, nut-side up, on a cake platter.  Spread half of the buttercream (about 1 1/2 cups) on the top, but not on the sides.  Top with a second cake layer, nut-side up.  Spread the top with the remaining 1 1/2 cups buttercream.  Top with the remaining cake layer, nut-side up. 
Gently toss the whole blackberries with the syrup in a mixing bowl.  Arrange the blackberries, stemmed sides down, on top of the cake.  The assembled cake with keep at room temperature, loosely covered, for 1 day.