- Split the half vanilla bean lengthwise. With the tip of a knife, remove the seeds from the pod. Set aside.
- In a saucepan off the heat, combine the sugar and cornstarch. Add the eggs and mix thoroughly with a whisk. Add the milk, vanilla seeds and pod. Bring to a boil over medium heat, stirring and scraping the sides and bottom of the saucepan, for about 8 minutes. Simmer gently for 1 minute.
- Remove from the heat. Remove the vanilla pod. Whisk in the yogurt. Pour the pastry cream into a bowl. Cover with plastic wrap directly on the surface of the cream. Refrigerate for 1 hour.
- Into each glass, spoon about 6 tbsp (90 ml) of the cream. Then, place two pieces of cookie dipped for approximately 2 seconds in the coffee into each glass. Cover with half the cream. Sprinkle with half the cocoa powder. Repeat with the remaining ingredients and end with the cocoa powder. Cover with plastic wrap and refrigerate between 2 and 12 hours before serving.