Sacher torte

Melt the bittersweet chocolate and let it cool a little.

Cream the room-temperature butter with the sugar on medium-high for a few minutes, until light and fluffy.

Add the egg yolks one at a time, then the vanilla extract; with the mixer on slow, drizzle in the cooled chocolate and mix until combined. Transfer to another bowl.

Whip the room-temperature egg whites on medium for two minutes to loosen them, then turn up to soft peaks.

Stream in the sugar while whipping, then whip about a minute more to a thick, stiff meringue.

Fold about a third of the meringue into the chocolate mixture with a metal-edged spoon to loosen it, then fold in the rest.

Fold in the cake flour in two batches, stopping as soon as it is incorporated.

Spread the batter evenly in a buttered and lined nine-inch springform pan.

Bake at 350F (180C) until firm on top; the time is transcribed as 'roughly 15 to 55 minutes'.

Bring the apricot jam and dark rum to a simmer in a pot and simmer about two minutes over medium heat to reduce a little; cool.

Once the cake is cool, cut it through the middle once with a serrated knife.

Spread a third to a half of the jam on the bottom layer, replace the top, and brush the top and sides with the remaining jam using a pastry brush.

Refrigerate until cold and set, around 30 minutes.

Melt the bittersweet chocolate and butter together in the microwave, about two minutes, or over a bain marie, and stir to emulsify into a runny glaze.

Set the cold cake on a rack over a baking tray, pour the glaze over from the middle outward to cover it completely, and patch the sides with an offset spatula.

Refrigerate another 30 minutes for the glaze to firm; pipe a name on top with leftover glaze if wanted, and serve with whipped cream.