Caramel Ice Cream Cake with Chocolate Ganache

To make the shortbreads, butter two 8-inch round cake pans and line with parchment paper. Over a sheet of waxed paper, sift together the flour, salt and cocoa powder. Set aside.

In the bowl of an electric mixer fitted with the flat beater, beat the butter on medium speed until creamy and smooth, about 2 minutes. Add the superfine sugar and continue beating until light and fluffy, about 5 minutes, stopping the mixer occasionally to scrape down the sides of the bowl. Beat in the vanilla until incorporated, about 1 minute. Reduce the speed to low, gradually add the flour mixture and beat just until blended.

Divide the dough evenly between the prepared pans. With dampened fingertips, press the dough evenly into the pans. Cover with plastic wrap and refrigerate for at least 30 minutes or up to 1 day.

Bake the shortbreads until the center is firm to the touch and the surface looks dull and dry, 25 to 30 minutes. Transfer the pans to a wire rack and let cool for 30 minutes.

Run a small spatula around the edge of each pan. Invert the pan onto a baking sheet and gently tap the pan bottom. Remove the pan, peel off the parchment and set the shortbread upright on the rack. Let cool completely.

Place the shortbreads in the freezer for 10 to 15 minutes. Let the ice cream stand at room temperature until soft enough to spread, about 5 minutes.

Place 1 shortbread, top side up, on a serving plate. Top with half of the ice cream, spreading it almost to the edges of the shortbread, then place in the freezer. Place the other shortbread, bottom side up, on a clean work surface. Top with the remaining ice cream, spreading it almost to the edges. Set the shortbread, ice cream side up, on top of the other shortbread. Cover with plastic wrap and immediately place in the coldest part of the freezer for at least 2 hours or up to 2 days.

To make the chocolate ganache, put the chocolate in a heatproof bowl. In a small saucepan over medium-high heat, bring the cream and salt just to a boil. Immediately pour over the chocolate. Using a whisk, stir until the chocolate melts and the mixture is smooth. Let cool to room temperature. Using a small offset spatula, spread the ganache over the top of the ice cream cake, allowing the ganache to drip over the sides. Freeze the cake until the ganache is set, about 10 minutes.

To facilitate slicing, dip a knife blade in hot water and wipe it dry before cutting each slice.