What is Tortenguss?

Tortenguss is the clear glaze poured over a German fruit flan: a thin, glossy layer that sets over the fruit and holds it in place. It is what stops the strawberries sliding off the Obstkuchen and stops them drying out by the next day.

It comes as a powder in small sachets, mixed with sugar and water and boiled briefly. The whole thing takes about three minutes, and it sets faster than most people expect the first time.

Clear or red

Two versions exist and the choice is aesthetic rather than technical.

Klar, the clear one, is the default. It disappears over the fruit and lets the colours show, which is what you want on mixed berries, peaches, mandarin segments or apple.

Rot, the red one, adds colour as well as shine, deepening red fruit into something glossier and more uniform. It is the traditional choice on a strawberry or raspberry flan, where it makes the fruit look the way a bakery window looks.

Neither changes the flavour much. If you are unsure, take the clear one.

How to make it

One unsweetened sachet sets 250ml of liquid. The method is on the packet and worth following precisely, because this is a recipe with no recovery once it starts setting.

• Stir the sachet together with two level tablespoons of sugar in a small pan.
• Gradually stir in 250ml of cold water, or fruit juice for more flavour, until smooth. Cold, and gradually, or it goes lumpy.
• Bring it to the boil while stirring, and boil briefly.
• Spoon it over the fruit immediately, working from the centre outwards.
• Leave it to set.

The part that catches people out

It sets fast. Not eventually, but while you are still holding the pan. That is the single most common complaint from anyone using it for the first time, and it is why the instructions say to work immediately and from the centre.

Three things make the difference. Have the flan built, the fruit arranged and the tin within reach before you turn the heat on. Spoon rather than pour, so the fruit does not float out of position. And do not stop to adjust anything halfway, because the glaze cooling in the pan is glaze you will not be able to spread.

If it does set too early, you cannot reheat it back to usable. Start another sachet, which is why the packs contain three.

Using juice instead of water

Swapping the 250ml of water for fruit juice is the easiest improvement. Apple juice is neutral and adds gloss, orange works on citrus and peach flans, and the syrup from a tin of fruit does the job well if you have drained one anyway. Keep the volume the same at 250ml, and keep the sugar unless the juice is already sweet.

How much one sachet covers

One sachet sets 250ml of liquid, which glazes a standard fruit flan base of about 28cm, or a large tart. For a deeper layer, or for fruit stacked rather than laid flat, two sachets and 500ml is the sensible move, mixed in one pan and applied in one pass rather than two.

Do not stretch a single sachet across more liquid to cover a bigger cake. The set is calibrated to the ratio, and a thinned glaze stays tacky instead of firming.

What it is not

It is not a jam glaze. Warmed apricot jam brushed over a tart does a similar job, but it is opaque, sticky and tastes of apricot. Tortenguss is nearly flavourless and sets firm rather than tacky, so a slice cuts cleanly.

What we stock

Our Dr Oetker Tortenguss Clear in the pack of three 12g sachets is the standard version, three flans' worth, unsweetened so you control the sugar.

It sits with the rest of the finishing products in our German cake decorations section.

The short answer

Tortenguss is the setting glaze for a German fruit flan. One sachet, two tablespoons of sugar, 250ml of cold liquid, boil briefly, then spoon over the fruit at once and do not dawdle.