Heat oven to 190C/gas mark 5. Grease and line a 20 x 30cm Swiss roll tin with baking parchment, then grease the parchment. Put the treacle, syrup, butter and grate the stem ginger in to a pan, heat until melted and stir to combine, then set aside to cool.

Put the eggs and sugar in a bowl and whisk for 10 minutes using an electric hand whisk until light, mousse like and doubled in size. The mixture is ready when it holds a ribbon trail from the beaters for 3 seconds. Sift over the flour, baking powder and spices, then pour the melted butter mixture around the sides of the bowl so that it trickles down into the whisked eggs.

Gently fold everything together. When just combined, pour the mixture into the Swiss roll tin and ease it into the corners. Bake for 12 mins until just cooked. While the sponge is cooking, lay a sheet of baking parchment, big enough to fit the cake, on your work surface and dust with a little sugar.

Once cooked, tip the cake directly onto the parchment. Use a serrated knife to score a line about 2cm from one of the shorter ends, making sure you do not cut all the way through. Gently roll up from this end, rolling the parchment between the layers. Leave to cool like this on a wire rack to help set the shape.

To make the icing, put the ingredients in a bowl and whisk until smooth. Transfer to a piping bag fitted with a large round nozzle, Unroll the sponge and drizzle the surface with the ginger syrup. Pipe a layer of ginger buttercream over the inside of the roll, then use the paper underneath to help tightly re-roll into a roulade. Slice off both ends for a neat finish.

Place the Log on a serving plate or board. Use the remaining icing to pipe a thick layer over the top of the sponge, zigzagging backwards and forwards to create a pattern. Decorate with white pearl sprinkles if you like.