1. Start with the custard. Add the milk to a small pot. Cut the vanilla bean pod lengthwise in half and remove the seeds. Add both to the milk and place on the stove – bring almost to a boil and let cool down again for at least 30 minutes.

2. Add the cornstarch and sugar to a small bowl, add a small amount of the cooled milk, and mix until well combined. Remove the vanilla bean pod from the milk and bring it back to a boil, add the cornstarch mixture and stir in. Continue stirring until the custard has thickened nicely. Let bubble for a minute, then remove from the heat. Mix in the egg yolk. Add a piece of plastic wrap directly on top of the custard to prevent skin from forming and let it cool down completely. This can be done a day in advance and the custard can be stored in the fridge until needed.

3. Preheat the oven to 350°F (180°C). Line a square 9 inches (23 cm) baking pan with baking parchment and grease lightly. Set aside. Brew the coffee and set it aside.

4. Add sugar (or xylitol), oil, eggs, and vanilla extract to a large bowl and mix light and fluffy. Add the yogurt and mix well. In a second bowl, mix the spelt flour with cocoa powder, baking powder, baking soda, and salt until well combined. Add to the large bowl in two batches, alternating with the coffee and mix until just combined – you do not want to overmix the batter. Pour into the prepared baking pan, break the Oreos into small pieces, and place on top of the batter. Bake for about 30-32 minutes or until a wooden skewer inserted into the cake comes out clean. Take out of the oven and let cool down completely (inside the baking pan).

5. Crush the Oreos with the help of a freezer bag and a rolling pin. You want fine crumbs. Set aside. Use the end of a wooden spoon or similar and poke holes into the cake (about 1 inch/2,5 cm apart). Prepare a piping bag with the vanilla custard – you might have to whip it first to get a pipe-able consistency. Fill the holes with the custard and spread the rest of the custard all over the cake. Sprinkle half of the crushed Oreos evenly all over the custard and place in the fridge for at least 2 hours or overnight.

6. Add the heavy cream to a bowl and whisk until slightly foamy. Add the confectioners’ sugar and cream stiffener and whisk until stiff peaks form. Next, add the remaining Oreo crumbs and fold them in. Spread this mixture evenly on top of the custard with the Oreo crumbs layer and smooth out the top. Place in the fridge for at least two hours. When ready to serve lift the cake out of the pan with the baking parchment, decorate with some Mini Oreos (optional), and cut with a warmed knife into (nine) pieces.