Preheat the oven to 230°C. Grease and line a 35 x 25cm Swiss roll tin.

Put the dates and 225ml of water into a saucepan, set over a low heat and bring to the boil.

Meanwhile, whisk the egg yolks and dark brown sugar in a kitchen mixer or a large bowl with an electric whisk, until the sugar has dissolved, then set aside.

Pour the dates and water into a blender and blitz to a fine purée.

Whisk the egg whites in a large bowl with an electric whisk until soft peaks form.

Now you’re ready to put it all together you need to work quickly. Add the vanilla extract to the sugar and egg mixture, then add the bicarbonate of soda and puréed dates and mix together. Fold in the flour and mix to combine, then beat in half the egg whites for 10 seconds. Beat in the remaining egg whites until fully incorporated.

Pour straight into the Swiss roll tin and smooth to the edges, then bake in the oven for 11–12 minutes until risen and golden-brown.

While the cake bakes, make the sauce. Put the cream, butter, brown sugar and bourbon into a saucepan set over a medium heat. Bring to the boil, whisking until smooth, then simmer for a few minutes until thickened.

Set a damp clean tea towel on a work surface and dust with the caster sugar. When the cake comes out of the oven, turn it top-down onto the damp tea towel and peel off the lining paper. Spoon one-third of the sauce over the sponge and gently roll the sponge up from the short side to form a fat roll.

Transfer to a serving platter, then spoon some more of the sauce over the top, and serve with the rest of the sauce alongside in a jug.