Spiced Sponge and Rhubarb Roulade

1 Preheat oven to 200°C. Grease a 26cm x 32cm swiss roll pan; line base with baking paper, extending the paper 5cm over the long sides.

2 Beat egg yolks and sugar in a medium bowl with an electric mixer 5 minutes or until very thick. Pour the hot water down inside of the bowl, add chocolate; gently fold in combined sifted flour and spices until just combined. Transfer to a medium bowl.

3 Beat egg whites in a medium bowl with an electric mixer until soft peaks form. Fold egg whites into chocolate mixture, in two batches, until just combined. Spread mixture into pan.

4 Bake cake 12 minutes or until golden and sponge springs back when pressed lightly with a finger.

5 Meanwhile, place a piece of baking paper, cut just larger than the pan, on a work surface; sprinkle evenly with extra sugar. Turn hot sponge onto sugar-covered-paper, peel away lining paper; trim crisped edges with a sharp knife. Working quickly, and using paper as a guide, roll sponge up from a long side. Cool for 5 minutes. Unroll sponge, remove paper; reroll, cover with a clean tea towel. Cool.

6 Meanwhile, make roasted rhubarb; combine ingredients in a medium bowl; transfer to a small shallow baking dish. Roast in oven for 10 minutes, stirring halfway, or until rhubarb is tender.

7 Unroll sponge; spread with mascarpone cream, leaving a 2.5cm (1-inch) border. Top with rhubarb. Reroll sponge to enclose filling. Serve roulade drizzled with rhubarb pan juices.

8 To make mascarpone cream, beat cream and mascarpone in a small bowl with an electric mixer until soft peaks form.