Gluten Free Swiss Roll Cake

all purpose gluten free flour (I used Better Batter)

xanthan gum (omit if your blend already contains it)

unsweetened natural cocoa powder

cornstarch

kosher salt

eggs (200 g, weighed out of shell) at room temperature, separated into yolks and whites

granulated sugar

unsalted butter, melted and cooled

warm water

Confectioners’ sugar, for rolling

Marshmallow creme (homemade or store-bought), for filling

semisweet chocolate, chopped

virgin coconut oil