Sacher Cake with White Chocolate

Ground almonds: buy them pre-ground if your kitchen doesn't have a food processor that'll do fine, dry grinding without turning them to almond butter — any oily nut ground too long turns into paste, and paste won't fold into batter evenly. If you're out, any finely ground nut with a neutral-to-sweet flavour works on the same principle — the job is fat and body, not almond flavour specifically, though hazelnuts will say so loudly.

Butter: room temperature means soft enough to take air when beaten with sugar, not melted — melted butter can't hold air pockets, and those pockets are part of what keeps this already-heavy batter from turning into a brick. Pull it out of the fridge an hour before, or if you forgot, a very short spell near (not on) a warm radiator does the same job without cooking it.

White chocolate, twice over — once melted into the batter, once as the glaze. For the batter, cheap white chocolate with vegetable fat instead of cocoa butter will still melt and still sweeten, but it won't set as cleanly in the glaze later, so if you're splitting a bar between the two uses, give the better one to the glaze, where its behaviour actually shows. For the glaze specifically, it needs to be chocolate that's mostly cocoa butter — that's what lets it melt smooth in hot cream and then set with a proper shine rather than staying greasy.

Strawberry jam: the acidity is the whole point, not a flavour note. A jam that's mostly sugar with a whisper of fruit will vanish under the white chocolate glaze and leave you a cake that tastes like one long sweet note with no edge. Use something with real fruit content — homemade, or a jam labelled with a high fruit percentage — and if strawberry isn't to hand, raspberry or sour cherry do the same structural job, sharpness against sweetness, better even, since they lean tarter.

Double cream and glucose syrup: double cream for fat content, which is what gives the set ganache body rather than a thin chocolate sauce. Glucose syrup you can leave out if you must — the cake will still work — but the glaze will be a touch less glossy and slightly more prone to going sugary if it sits a day or two. A spoon of liquid honey does something similar, though it'll bring its own flavour along, which isn't nothing in a cake this sweet already.

Some say Sacher cake has to have apricot jam and dark chocolate or it isn't Sacher — no, because the name travelled a lot further than the original recipe did, and what made it famous in Vienna was never a locked formula, it was a hotel's name on a cake good enough to be worth copying badly for a century. What you're making here keeps the construction — sponge, cut, jam, pour, set — and swaps the flavour register from bitter-and-sharp to sweet-and-sharp. That's a different cake wearing the same coat, and there's nothing wrong with that; just don't expect the Hotel Sacher to send flowers.

On patience: let the sponge cool fully before you slice it, not warm-ish, fully — a warm sponge is still setting its crumb, and a knife through it drags and tears instead of cutting clean layers. The same goes for the glaze sitting in the fridge for those twenty minutes: that's not downtime, that's the glaze actually becoming the texture you want instead of a liquid pretending to be one. In a domestic kitchen without a blast chiller, time at a steady cold is the only tool you have for that — don't rush it by cranking the freezer, because an uneven fast chill can crack a thin glaze shell rather than set it evenly.