[Hungary] How to cook Chimney cake with nutella (kürtoskalács)

Ingredients
- 2 x 7 g sachets dried yeast
- 200 ml lukewarm milk
- 275 g (1¼ cups) caster sugar
- 3 egg yolks
- 150 g unsalted butter, melted
- 500 g (3⅓ cups) plain flour
- vegetable oil, to brush
- 330 g (1 cup) Nutella, warmed
- cocoa powder, to dust