Preheat the oven to 180 °. Grease the weck jars or twist-off jars and sprinkle with breadcrumbs.
Mix the eggs and sugar together until the sugar has dissolved. Add oil and Baileys and stir. Stir in the chocolate flakes, flour and baking powder. Half fill the jars with the batter and bake for 40 minutes. At the end of the baking time, take the jars out of the oven and close them immediately to create a vacuum.
The specified amount is also sufficient for a 30 cm springform pan.