Black Joe Cake with Salted Caramel Filling & Mocha Mascarpone Frosting

Makes one 9-inch 2-layer cake
Serves 8 (or 10 skinny people)

Ingredients
For the cake:
2 cups cake flour (you can substitute all-purpose flour per the following: 1 cup cake flour = 1 cup all purpose flour minus 2 tablespoons)
3/4 cup unsweetened cocoa powder
1 1/2 teaspoons baking soda
3/4 teaspoon salt
3/4 cup (6 ounces) unsalted butter, room temperature
2cups (packed) golden brown sugar
3 large eggs
1 1/2 teaspoons vanilla extract
1 cup buttermilk (to substitute, measure 2 tablespoons of vinegar in a measuring cup. Add enough full-fat milk to measure one cup. Stir and let sit for 5 minutes)
4 teaspoons instant espresso powder dissolved in 3/4 cup hot water (not instant coffee!)
For the salted caramel filling:
3/4 cup (6 ounces) unsalted butter, room temperature
1 teaspoon fleur de sel
1/2 cup caramel
3 cups sifted powdered sugar
For the Mocha Mascarpone Frosting:
1/3 cup unsweetened cocoa powder
1 tablespoon instant espresso powder (not instant coffee!)
1 1/2 cups chilled heavy whipping cream, divided
1 1/3 cups sugar
28 ounces chilled mascarpone cheese

Directions

Preheat to 325 degrees F. Grease two 9-inch cake pans with 2-inch-high sides.  Add about two tablespoons of flour to the greased pan to coat, tapping out any excess. Repeat with second cake pan.  Line bottom of pans with parchment paper. 
 
Sift 2 cups cake flour, cocoa, baking soda, and salt into medium bowl.   Be sure to whisk the dry ingredients after you've sifted.  Using an electric mixer, beat butter in large bowl until smooth. Add brown sugar and beat until well blended, about 2 minutes.  Add eggs 1 at a time, beating well after each addition. Mix in vanilla. Add flour mixture in 3 additions alternately with buttermilk in 2 additions, beating just until blended after each addition. Gradually add hot espresso-water mixture, beating just until smooth.  Divide batter between pans; smooth tops.  Bake cakes until tester inserted into center comes out clean, about 40 minutes. Cool cakes in pans on rack 15 minutes.  Run small knife around sides of pans to loosen cakes. Invert cakes onto racks; lift pans off cakes and remove parchment.   Place wire rack atop each cake; invert again so top side is up. Cool completely.
 
To prepare the Salted Caramel Filling:
Beat the butter and salt in the bowl of a stand-up mixer until light and fluffy, about 4 minutes.  Reduce speed to low and add sugar.  Beat until just incorporated. Turn off your mixer, scrape down the sides and add the caramel.  Turn on mixer and beat until light and fluffy.
To prepare the Mocha Mascarpone Frosting:

Sift cocoa powder into large bowl; add espresso powder. Additionally ALWAYS sift your cocoa as well.  Bring 1 cup cream to boil in small saucepan. Slowly pour cream over cocoa mixture, whisking until cocoa is completely dissolved, about 1 minute. Add 1/2 cup cream and sugar; stir until sugar dissolves. Chill until cold, at least 2 hours.  Add mascarpone to chilled cocoa mixture. Using electric mixer, beat on low speed until blended and smooth. Increase speed to medium-high; beat until mixture is thick and medium-firm peaks form when beaters are lifted, about 2 minutes (do not over beat or mixture will curdle). 

Assembly:

Using pastry brush, brush off crumbs from cakes. Place 1 cake layer, top side up on a cake platter.

Typically I buy disposable cake boards which make the cake easier to move, especially if you will be frosting on a revolving cake stand and then moving to a cake saver. This time around I forgot to buy one so instead I used the removable bottom from my tart pan. Worked great, just doesn't look as pretty.

Spoon the Salted Caramel Filling in dollops over top of cake (I used the entire bowl of the salted caramel, was A LOT but it was gooood). Using offset spatula, spread frosting to edges.

Top with second cake layer, top side up, pressing to adhere. Spread thin layer of frosting over top and sides of cake. Chill 10 minutes. Using offset spatula, spread remaining frosting over top and sides of cake, swirling decoratively.
Garnish with chocolate curls or sprinkles, or simply leave as is. This cake is so good it doesn't need accessories! I'd let the cake chill in the fridge for at least an hour prior to cutting so the frosting firms up. This allows for a cleaner cut through the cake and removal.
 
Cake and Mocha Mascarpone Frosting recipe courtesy of Bon Appetit