Mum's Sunday Tea Lemon Curd Swiss Roll

145g slightly salted butter, diced
145g superfine sugar
finely grated zest and juice of 2 large unwaxed lemons
2 medium eggs, at room temperature, beaten to mix
3 medium eggs plus 1 yolk, at room temperature
160g superfine sugar, plus extra for sprinkling
160g self-rising flour
1 large baking sheet, 10 x 15 inch, greased with butter and line with parchment

Lemon Curd

Put the butter and sugar into a large heatproof bowl (double boiler) and add the lemon zest and juice.

Set the bowl over a pan of gently simmering water (don't let the base of the bowl touch the water).

Heat, stirring frequently with a wooden spoon, until the sugar has completely dissolved.

Strain the beaten eggs into the mixture.

Stir constantly until the mixture becomes very thick and opaque.

As soon as you can draw a finger through the mixture on the wooden spoon and make a clear path, remove the bowl from the pan (keep the pan of hot water for later).

Pour the lemon curd into a smaller heatproof bowl.

Leave to cool, then cover with plastic wrap and chill.

Sponge

Preheat your oven to 375°F.

Wash and dry the large heatproof bowl used earlier.

Put the 3 whole eggs and the yolk in the bowl.

Whisk together, just to mix, using an electric hand mixer or rotary whisk.

Whisk in the sugar.

Set the bowl over the pan of gently simmering water and whisk for about 3 minutes until the mixture is thick and feels lukewarm when you dip in your little finger.

Remove the bowl from the pan and set it on a heatproof surface.

Continue whisking until the mixture has returned to room temperature and is thick enough to leave a ribbon-like trail when the whisk is lifted.

Sift the flour onto a sheet of waxed paper.

Sift the flour again onto the whisked mixture.

Gently, but thoroughly, fold in with a large metal spoon or plastic spatula.

Tip the mixture onto the prepared baking sheet and spread evenly, leaving a half-inch border all around, between the sponge and the edges of the baking sheet.

Bake in the heated oven for 8-9 minutes until the sponge is a good golden brown and the middle springs back when gently pressed.

While the sponge is baking, lay a large sheet of parchment (slightly large than your baking sheet) on the work top and sprinkle it with superfine sugar.

Assemble

When the sponge is baked, tip it onto the sugared paper and lift off the baking sheet, then carefully peel off the parchment.

Spread the lemon curd evenly over the sponge.

Working quickly trim off the edges of the sponge with a sharp knife.

Make a deep cut about 1/2 inch from one short edge, then fold this edge quite tightly – it will be the center of the roll.

Using the sugared parchment to help you, roll up the sponge from this end.

Leave the parchment wrapped around the sponge roll to keep the shape.

Transfer to a wire rack and leave to cool.

When the sponge is cold, remove the parchment.

Dust the Swiss roll lightly with superfine sugar and set it on a serving plate.

Collister, Linda. The Great British Bake Off Big Book of Baking. Page 152-153. BBC Books, 2014.