Prepare the ingredients
Add pumpkin seeds and 60g (1/4 cup) sugar to your blender or food processor. Blitz to get a fine powder. Sift into a bowl and add the baking powder. Preheat your oven to 180 °C / 355 °F. Separate your eggs yolks from egg whites. Add the egg yolks to a bowl of a stand mixer (or to a large bowl if you are using an electric mixer). Add the egg whites to a separate clean bowl.
Beat the eggs
Add about 3 tbsp of sugar to the egg yolks and beat with the electric mixer (or using a stand mixer) on medium speed for about 5 minutes to get a nice, fluffy and pale mixture, then add the pumpkin seed oil and incorporate well. Add the rest of the sugar to the egg whites and beat until you get soft peaks. Alternate adding dry ingredients (pumpkin seed mixture) and egg whites to the egg yolk mixture. Gently fold in the ingredients with a spatula before adding the next portion of ingredients.
Generously grease a large 30 x 40 cm (12 x 16 inch) baking sheet with butter, then place the parchment paper on top of it to stick. Pour the swiss roll batter to the baking sheet, evenly spread. Make sure there are no lumps. Place in the preheated over and bake for 15 minutes at 180 °C / 355 °F.
Remove the baked swiss roll cake from the oven and transfer it along with the parchment paper on the working surface. Place another sheet of parchment paper on top of the cake and roll into a roulade. Then roll the roulade in a kitchen towel and let it cool completely, for about 30 minutes.
Add the filling and roll
When the cake is completely cool, combine the sour cream and mascarpone in a bowl. Stir well to combine. Unroll the cake - it’s okay if it curls up a bit. Add the filling and spread it evenly over the cake, leaving about 5 cm (2 inches) at one of the shorter sides as the cream will pile up when rolling. Roll the cake into a roulade. Start rolling on the opposite side of that 5 cm (2-inch) space. The cream will be light and you might feel it’s not creamy enough but there’s nothing to worry, after some time in the fridge it will be perfect. Wrap in plastic wrap or parchment paper and place in the fridge for at least 30 minutes or even better overnight to firm. Slice and serve.