• Preheat the oven to 180'C and line a 39 x 24cm Swiss roll tin with a sheet of baking paper.
• Separate the eggs and then add the egg whites into a large metal bowl. Whisk with an electric mixer until they start to form stiff peaks - this is the point where you could tip the bowl upside-down over your head and they won't fall out!
• Gradually add the caster sugar while continuing to whisk, until the egg whites form glossy peaks. You know it's done when you can rub a tiny bit of the mix between your fingers and it doesn't feel grainy.
• Beat the egg yolks together in a small bowl then pour into the egg whites. Use a spatula to fold them in - streaks are fine, just make sure you don't knock the air out the mixture so go gently.
• Mix the flour, baking powder and xantham gum together in a bowl the sieve into the mix. Fold in using your spatula again until there are no lumps of flour.
• Gently pour the mix into your lined tin and smooth out using a spatula. Bake in the centre of the oven for 10-12 minutes. You want the sponge to be springy and lightly golden but not too dark - if you over-bake it, it will be more likely to crack when you roll it.
• Place the tin on a cooling tray for a minute or so. Meanwhile lay out a thin tea towel and lightly dust with some extra sugar.
• After a minute, gently tip the tin upside-down onto the sugared-towel. Peel off the baking paper, going slowly so you don't rip the sponge.
• Using a knife, score a line approximately 2-inches in from one of the short edges of the sponge. Then use the tea towel to guide the sponge, to roll it up into a spiral, starting at the scored end. Once rolled, wrap tightly in the tea towel and leave to cool completely (around one hour).

To assemble your Swiss roll:

• To make the cream filling, pour the cream into a large bowl and whisk using an electric mixer until it forms soft peaks - this may take 5-10 minutes so be patient!
• Once the cream has thickened to soft peaks, stop the mixer and add the lemon curd. Continue to whisk until the cream thickens to a texture where you can spread it and it will hold its shape.
• Very gently, unwrap the sponge and then carefully unroll it. Use a spoon to loosen the jam and then it in an even layer all over the sponge. Next spread the whipped lemon cream on top, using a palette knife.
• Carefully roll the sponge back the same way as before, a little more loosely this time so as not to squish the filling out everywhere. Sprinkle with a little icing sugar and serve!