1 Stir the yeast and 70ml lukewarm water in a bowl to combine and stand until the mixture begins to foam (5-7 minutes).
2 In an electric mixer with a dough hook, combine the flour, castor sugar, butter, cocoa powder, eggs, salt and yeast mixture. Add the milk and knead on low speed until a sticky dough forms (4-5 minutes, the dough will be quite wet). Turn out onto a lightly floured surface and dust the top with a little extra flour. Shape into a ball, transfer to a greased bowl, cover with plastic wrap and stand in a warm place until doubled in size (1-1½ hours).
3 Turn the dough out onto a floured surface and roll to 1,5cm thick. Cut out rounds with a floured 8cm-diameter cutter, then cut out holes with a 2,5cm-diameter cutter. Place 2cm apart on baking sheet lined with baking paper, cover and stand until doubled in size (45 minutes to 1 hour). Reroll scraps and repeat.