For the cake:
2 cups cake flour
2 tsp baking powder
1/8 tsp baking soda
¼ tsp salt
1 ¼ sticks (10 tablespoons) unsalted butter, room temperature
1 cup sugar
3 large eggs
1 large egg yolk
1 ½ tsp pure vanilla extract
¾ cup buttermilk

For the espresso extract:
2 tbs. instant espresso powder
2 tbs. boiling water

For the espresso syrup:
½ cup water
1/3 cup sugar
1 tbs. amaretto, Kahlua, or brandy

For the filling and frosting:
1 8-oz. container mascarpone cheese
½ cup confectioners sugar, sifted
1 ½ tsp pure vanilla extract
1 tbs. amaretto, Kahlua, or brandy
1 cup cold heavy cream
2 ½ oz. bittersweet or semisweet chocolate, finely chopped, or about ½ cup store bought mini chocolate chips

Chocolate covered espresso beans, for decoration (optional)
Cocoa powder, for dusting

Getting ready: Center a rack in the oven and preheat the oven to 350 degrees F. Butter two 9 x 2 inch round cake pans, dust the insides with flour, tap out the excess and line the bottoms of the pans with parchment or wax paper. Put the pans on a baking sheet.

To make the cake: Sift together the cake flour, baking powder, baking soda and salt.
Working with a stand mixer, preferably fitted with a paddle attachment, or with a hand mixer in a large bowl, beat the butter on medium speed until soft and creamy. Add the sugar and beat for another 3 minutes. Add the eggs one by one, and then the yolk, beating for 1 minute after each addition. Beat in the vanilla; don’t be concerned if the mixture looks curdled. Reduce the mixer speed to low and add the dry ingredients alternately with the buttermilk, adding the dry ingredients in three additions and the buttermilk in two (begin and end with the dry ingredients); scrape down the sides of the bowl as needed and mix only until the ingredients disappear into the batter. Divide the batter evenly between the two pans and smooth the tops with a rubber spatula.Bake for 28-30 minutes, rotating the pans at the midway point. When fully baked, the cakes will be golden and springy to the touch and a thin knife inserted into the centers will come out clean. Transfer the cakes to a rack and cool then for about 5 minutes, then run a knife around the sides of the cakes, unmold them and peel off the paper liners. Invert and cool to room temperature right side up.

To make the extract: Stir the espresso powder and boiling water together in a small cup until blended. Set aside.

To make the syrup: Stir the water and sugar together in a small saucepan and bring just to a boil. Pour the syrup into a small heatproof bowl and stir 1 tablespoon of the espresso extract and the liqueur or brandy; set aside.

To make the filling and frosting: Put the mascarpone, sugar, vanilla and liqueur in a large bowl and whisk just until blended and smooth. Working with the stand mixer with the whisk attachment or with a hand mixer, whip the heavy cream until it holds firm peaks. Switch to a rubber spatula and stir about one quarter of the whipped cream into the mascarpone. Fold in the rest of the whipped cream with a light touch.

Links to the other posts on Tiramisu cake: 

Smitten kitchen: Tiramisu cake
Whist: a food blog: TWD Tiramisu cake
Cooking for Engineers: Simple Tiramisu