Separate eggwhites from the yolks and beat them until they form a firm peak (When you turn the whisk upside down eggwhites should hold, but the tips should fold back.)
Add sugar and beat for a minute or two.
Add egg yolks and beat them in.
Add flour, poppy seeds and lime zest and use the lowest setting of the mixer to fold it in or use a spatula and do it manually.
Transfer the mixture to the baking tray and bake for 10 minutes.
Remove from the oven. Place a clean tablecloth on a flat surface and place the baked sponge on the tablecloth top side down, leaving the baking paper on. Roll in the cloth.
Cold method: In a big bowl cover elderflower heads with whipping cream and leave to infuse for 24 hours in the fridge. After 24 hours run the cream through a fine sieve to remove the elderflower heads.
Warm method: Place elderflower and cream into a pot and cook on low heat for ten minutes. Don't let the cream boil! Leave to cool to room temperature, then remove the elderflower heads and leave in the fridge overnight.
Whip the cream just befor entirely firm.
Use a fork to cream the mascarope cheese.
Add mascarpone and honey to the whipped cream and use the lowest settng to incorporate it in the whipping cream.
Add lime juice and use a spatula to mix it in.
Once the sponge is cool unroll and carefully remove the baking paper.
Juice 2 -3 limes and use the juice to soak the sponge.
Frost with elderflower mascarpone cream and tighly roll.
Leave in the fridge for an hour for easier cutting.