Preheat oven to 200°C/390°F (fan oven 180°C/360°F). Line a large baking pan with parchment paper.
Separate egg yolks from the whites. Beat egg whites in a bowl until soft peaks form. Then, add sugar and egg yolks, one by one while beating the mixture. Sift in the flour and fold it in with a spatula, and add lemon zest and poppy seeds. Pour the mixture in the baking pan and level it out evenly. Place in the preheated oven and bake for about 10 minutes, or until golden brown.
Remove cake from the oven, and carefully turn it over on a clean kitchen towel. Remove the baking paper and roll the cake in, towel included, and let it cool down completely (about an hour).
While the cake is cooling, prepare the lemon cream: whisk the whipping cream. In a separate bowl, mix mascarpone with icing sugar, lemon zest and lemon juice. Fold in the whipped cream and combine.
Roll out the cake, remove the towel. Spread the lemon cream over the cake in an even layer and roll in into a roulade again. For a nicer finish, cut away the edges off the roll to reveal an even center.
To decorate the cake, mix together icing sugar and lemon juice into a runny but thick sauce. Drizzle the sauce over the roll and let it firm. Top the roll with fresh strawberries. You can also add some edible flowers and fresh thyme.