For the Sacher-style tartlets, first beat the butter with sugar and vanillin sugar for the sand mixture using a hand mixer (stirring sticks). Stir in the yolks one by one. Stir in the chocolate coating with the breadcrumbs using a wooden spoon. Beat egg whites until stiff and fold in.
Pour the mixture into a greased, floured muffin tin and smooth out. Place the pan on the rack in the lower half of the preheated oven.Top/bottom heat: 180 °Hot air: 160 °CBaking time: approx. 35 min.
Turn out the cooled muffins onto a cake rack covered with baking paper. Cut the cooled muffins 1 time horizontally.
For the jam filling, whisk the jam until smooth. Assemble the muffins with it and place them on a baking paper.
For the chocolate icing, put water with sugar in a saucepan and boil until sugar is dissolved. Remove from heat, let cool for about 5 minutes and stir in the chocolate glaze. Frost the cupcakes with the glaze.
For piping and decorating, whip whipped cream with vanillin sugar and cocoa until stiff. Place in a piping bag with a star-shaped nozzle (8 mm Ø) and pipe rosettes onto the tartlets.
Decorate the Sacher-style tartlets with chocolate hearts before serving.