Preheat the oven to 180C/350F/Gas 4. Grease a 10x15-inch cake roll pan, and line the base with parchment paper.
Using a handheld or stand mixer fitted with the whisk attachment, whisk the egg whites until stiff peaks form. Set aside.
In a separate bowl, beat the egg yolks and sugar until light and thick. Beat in the vanilla, yogurt and molasses. Add the flour, baking powder, spices, and salt, and mix until combined. Gently fold in the whipped egg whites.
Pour the batter into the prepared pan, and spread out evenly. Tap the pan lightly on the surface a few times to level out the batter. Bake for 8 - 10 minutes or until the cake springs back when lightly touched.
Immediately invert the cake onto a tea towel dusted generously with icing/powdered sugar. Leaving the parchment paper on, roll the cake up with the tea towel, starting at a short end. Allow to cool completely on a wire rack.
For the Filling
Using a handheld or stand mixer fitted with the whisk attachment, whip the heavy cream until it starts to thicken. Add the icing sugar, vanilla, and spices, and whip to stiff peaks.
Unroll the cake, peel off the paper, and spread the whipped cream evenly over the cake. Re-roll without the tea towel. Cover and refrigerate for at least 1 hour. Dust with icing sugar and serve.
Notes
Make sure the cake is HOT straight from the oven before rolling. The cooler the cake, the more likely cracks will form whilst rolling.*Light or true molasses is much sweeter than blackstrap molasses (which is very bitter), and is much preferred in baking. Black treacle is also fine to use.**Make your own cake flour! Measure out 1 and 1/4 cups (156g) of plain/all-purpose flour, remove 2 tablespoons and replace with 2 tablespoons of cornflour/cornstarch. Sift well.Make ahead of time: Prepare the cake as instructed, then cover and refrigerate the filled cake for up to 1 day.Prepared cake roll, with filling, freezes well for up to 2 - 3 months. Thaw overnight in the fridge before slicing and serving.