Single or double

Friends of Erre4m, welcome back to our blog. I am Enrico Gumirato and today we are going to talk about the methods for preparing sponge cake. 

In the previous posts we talked about sponge cake, its basic ingredients and their functions.

In this second instalment I would like to focus with you on the preparation methods: there are essentially two of them, and they differ essentially in how you treat the eggs which, as I mentioned last time, are the main ingredient. Before getting into the merits of each method, let's take a closer look at the characteristics of eggs.

The nutrients in an egg are mainly water, proteins and fats, with a small share of mineral salts and carbohydrates.

Here is the percentage breakdown:

As you can see from the chart, whole eggs and yolks contain the same constituents, albeit in different percentages, while the egg white contains water, proteins, carbohydrates and mineral salts. This difference is of fundamental importance: the egg white is in fact the part of the egg with the greatest whipping power, because it contains no fat. Fat does indeed significantly limit the foaming power of the proteins in the whole egg, and above all those of its white part. It is interesting to note, however, that if we add fat to the egg white in excess of 10% of its weight, its proteins react and start bonding again — which is why the whole egg has good whipping power. As for the yolk, it manages to incorporate a considerable amount of air (though not comparable to the white) thanks both to its proteins (a full 18%) and, above all, to its emulsifying action due to the lecithins it contains.

In the light of all this, here is the theme of our discussion: single whipping or double whipping? 

Let's see what it involves.

Single or separate whipping?

Single whipping means the classic way of preparing sponge cake: whipping the whole eggs with the sugar and then folding in the flour. With this method I get a product that is on the one hand less aerated, because the fats in the yolk tend to inhibit the whipping power of the egg-white proteins; on the other hand, though, the air bubbles incorporated into the mass will be proportionally larger, and the end result is a product with a visibly open crumb.

With separate whipping, as the name itself suggests, you separate the yolks from the whites and whip them individually (with sugar added to both). Once maximum volume is reached, the two masses are gently folded together. The flour can be added in two ways: either to the yolks first, before folding in the whites, or last of all, once the two whipped masses have been combined. This system includes, first and foremost, two ancient preparations that are the founding parents of this sweet base: Lady torta Savoia and Sir Savoiardo (the ladyfinger). By whipping yolk and white separately I obtain their maximum volume of foam — very small bubbles, with the final effect of a very soft yet more compact cake; in fact, this system is by far the most used for sponge cakes meant to be rolled (pasta dobos, charlotte, biscuit, etc.), as it lends itself very well to being worked “in sheets”. Baking, in this case, since the preparation is very thin, must be done at a higher temperature and for just a few minutes (200–210 °C for 7–8 min).

And as usual, here is the recipe at the bottom of the page. 

The torta Savoia

The torta Savoia, which you can make either in a cake tin or in sheets

Quantities for an 18–20 cm cake or about 3 sheets of 30x40 cm, 5 mm thick

90 g     fresh egg whites at room temperature

60 g     fresh egg yolks

120 g   caster sugar

50 g     potato starch

30 g     white flour

Flavourings   vanilla and a dash of bitter almond

Proceed as explained above, flavouring the yolks, which should be whipped for 12 min with 100 g of the sugar.

Then GENTLY fold in the dry ingredients, sifted 2–3 times. 

And last of all the egg whites, whipped with the remaining 20 g of sugar to ALMOST FIRM peaks, because over-whipped egg whites turn grainy and are difficult to combine with the rest of the recipe.

Baking: 170 °C for the cake, 200 °C for the sheets.

HAPPY BAKING!

(Blog edited by Enrico Gumirato, pastry chef and trainer)