These extra soft, very delicious 5 layer cocoa slices are a very simple, nothing special confection; they look like wafer biscuits, though they aren’t made of thin and crispy wafer, but a soft, kneaded dough. What makes these cake layers a bit odd is the leavening agent which is an uncommon ingredient: it’s ammonium bicarbonate or szalalkáli/szalagáré as we call it in Hungary. My granny often used it because ammonium bicarbonate gives pastries an extraordinary, very light and airy texture that can’t be reproduced by baking powder or soda.
Ammonium bicarbonate was the forerunner of today’s baking powder and baking soda, it was the sole leavening agent for a long time. It’s the bicarbonate salt of the ammonium ion, a white powder which makes cookies and pastries very light, crisp and somewhat fluffy. Don’t confuse this with ordinary household ammonia, which is a poisonous substance and should not be used with foods or baked goods.
Ammonium bicarbonate has to be dissolved in liquid before adding to the dough. It’s typically used with smaller or thin baked goods that can quickly evaporate the ammonia gas as it builds up within the baked item. During the baking process, an ammonia aroma fills your kitchen – for this reason cross ventilation is deeply recommended, but it will not remain and can’t be noticed in the baked goods when they are eaten.
For the dough:
- 500 g (~4 cups) flour
- 150 g (~5 1/3 oz) lard
- 1 egg
- 50 g (~1/4 cup) sugar
- 150 ml (~2/3 cup) milk
- 15 g (~1/2 oz) ammonium bicarbonate
For the filling:
- 1 liter (~4 1/4 cups) milk
- 200 g (~1 2/3 cups) flour
- 200 g (~1 1/2 cups) powdered sugar
- 50 g (~1/2 cup) cocoa powder
- 120 g (~1/2 cup) butter
Size of the baking tray: 33×33 cm (13×13 inch)
First make the filling. Place flour, cocoa powder and half of the powdered sugar in a sauce pan and whisk together. Stir milk in small batches into the dry ingredients to avoid lumps. When all the milk has been added, set the saucepan over medium heat and cook while stirring constantly until the cream thickens. Set aside and let it cool completely.
Cream the soft butter with the remaining powdered sugar. Set aside.
Dissolve ammonium bicarbonate in milk. Sift the flour into a bowl, add sugar, egg, lard and milk with ammonium bicarbonate. Mix them up and knead into a pliable dough. Divide the dough into 5 equal parts.
Preheat the oven to 180°C / 356°F. Grease a baking tray.
Onto a floured surface roll out the first piece into a thin rectangle. Transfer onto the baking tray, poke top with a fork and bake for 8 minutes. Repeat process with the remaining dough balls.
Once the filling and cake layers are all cool, assemble the cake. Combine creamed butter with the thick cocoa filling thoroughly until fully incorporated. Place a cake layer on the clean baking tray, spread one fourth of the filling on top evenly, and then repeat till the last cake layer. Chill in the fridge overnight to allow the cake layers to soften.