If making the rose sugar (optional), place the petals in a food processor with the sugar and blend to a crumb-like texture. Place it on a large, shallow tray and leave it to try in the sun. When it has dried out to a sugar, store in a sterilized jar (see below).

Line a 35 x 30cm (14 x 12in) baking tray with baking parchment and butter it.

Whisk the eggs and the 125g (4½oz) of sugar until pale yellow. In a separate bowl, sift together the flour and baking powder; t his is very important to get the super-light texture. Fold the flour into the egg mixture, then fold in the milk. Pour into the prepared baking tray and spread it out evenly. Bake for 5–8 minutes, then place on a wire rack in the tin, just until cool enough to handle.

Place a piece of baking parchment on a work surface and sprinkle it with the remaining 2 tablespoons of caster sugar. Flip the sponge on to the sugar-sprinkled paper, peel the used baking parchment from the sponge and leave to cool completely.

Whisk the butter until soft and fluffy, add the icing sugar and whisk into a light cream. Blitz the jam in a food processor so it becomes like a paste, then fold into the buttercream.

When the sponge is cold, spread the buttercream evenly over it, then roll it up from one of the long sides into a roulade. Wrap tightly in baking parchment and leave to chill in the refrigerator for at least 1 hour, or until the next day.

To serve, whip the cream, put it in a piping bag, then pipe little dots all along the length of the roulade. Sprinkle with rose sugar and take to the cake table.

To sterilize jam jars: preheat the oven to 160°C/140°C fan/325°F/Gas 3. Wash the jars and their lids in hot soapy water, then place on a baking tray lined with baking parchment or a silicon liner and place in the oven for 20 minutes. Switch off the oven off, leaving the jars inside.