ترايفل الشوكولاته

Combine powdered milk, sugar, oil, water, and cocoa powder in a pot.

Bring the mixture to a boil over medium heat until thickened.

Gradually add vanilla and egg yolk while whisking continuously.

Pour a small amount of hot mixture over the yolk and whisk until combined.

Return the yolk mixture to the pot and boil for an additional 2 minutes.

Mix cream with sugar to taste in a separate bowl.

In a large glass bowl, add a layer of biscuits, then cover them with a layer of chocolate sauce, then add the filling, then another layer of biscuits and chocolate, and finally add a layer of whipped cream.

Garnish the trifle with grated chocolate or chocolate chunks or cocoa powder.