Following various experiments in the kitchen lab (muahaha) I’ve discovered my ideal sugar-free sponge with the birch sugar substitute xylitol. It’s a genoise whisked over heat. Although very slightly dry it has a lovely texture and worked beautifully in concoctions like my healthier mini Swedish princess cakes and Fraisier (strawberry cake) which are filled with cream and/or creme pat. It’s a super light sponge.
It’s not difficult to make a genoise sponge but here are some tips to help avoid possible disasters:
- Make sure your ingredients are fresh and your flour isn’t old. It’s best to use free-range eggs.
- Start whisking the yolks and sugar immediately they’re together because if you don’t the sugar starts to ‘burn’ the yolks and lumps form.
- Avoid overheating your eggs at the earlier stage or you’ll get scrambled eggs (a genoise is not based on scrambled eggs, though this could be an interesting experiment). For the bain marie the bowl should fit nicely on the saucepan. There should only be a little water in your pan (1 or 2 cm/1/4 inch) and it shouldn’t touch the bowl. The water should be hot so you can see the steam coming up or on a very low simmer, but it should not be boiling. Take off the heat for a while if necessary, or lower the heat. Whisk the eggs constantly.
- Make sure your genoise batter actually doubles or triples in size and gets to a very thick ribbon stage. Don’t stop earlier because your arm is tired – learn to switch arms and use your left one if you’re whisking manually.
- At the stage where you fold in the flour do not overmix or overfold. When the flour is just incorporated stop and your batter will stay light and fluffy. Overwork and your cake will flatten out and become heavy.
Keep all that in mind and you’ll get the perfect genoise!
- Grind the xylitol with a barmix or coffee grinder to the texture of caster/superfine sugar (more or less) but not as fine as icing/powdered sugar. This will make the texture of your genoise sponge nicer. You can use golden or white caster/superfine sugar if you prefer.
- Preheat your oven to 180°C/350°F (static, non-convection oven) or 160°C/320°F (fan-assisted convection oven)
- Line your baking tray (30cm x 40cm/16in x 12 in) with baking paper, or butter and flour your cake tin
- 80g/two-thirds of a cup plain/all purpose flour – good quality ‘cake’ flour works best (French T45)
- 20g/2 tablespoons cornflour
- 40g/a third of a cup ground almonds
- 4 medium to large-sized eggs (about 230-240g)
- 120g/half a cup ground xylitol (birch sugar substitute) or caster/superfine sugar
- a pinch of salt
- a knife-tip of vanilla powder or scraped seeds from a quarter of a vanilla pod (optional)
- In a medium-sized bowl whisk the flour, cornflour and ground almonds together to combine.
- Whisk the yolks and ground xylitol (or sugar) in a large metal or glass bowl for a few minutes then place on a bain marie.
- Whisk over heat until the batter doubles or triples in volume, thickens to ribbon stage and reaches a temperature of 45°C/113°F. This can take up to 20 minutes or more.
- When it reaches this temperature take off heat.
- Whisk in the salt and vanilla.
- Whisk until the cake mixture cools (the bottom of the bowl should feel cold when you touch it with your hand). You can whisk by hand (around 15 mins) or on your stand mixer (5-10 mins).
- Add half of the flour in a stream and fold it in gently with a rubber spatula or metal spoon with a hole(s) with slow figure of eight motions, going through the middle then round the sides. When it’s starting to combine add the other half of the flour. Don’t overmix and stop when the flour is just incorporated.
- Pour into your cake tin or on your tray (spread with the minimum of movements possible with a metal spatula).
- Bake in the middle of the oven for 22 to 25 minutes (round cake tin) or 10 to 15 minutes (swiss roll or baking tray) till it’s golden, a skewer comes out clean when inserted in the middle and the top springs back a little when you press it lightly with a finger.
- Take out, remove from the mould and allow to cool on a wire rack before cutting, filling or assembling.
Yay! You have a lovely genoise sponge. Have fun making cakes with it! 🙂