Stir together the yeast, 1 tablespoon of lukewarm water and half the flour in a bowl and allow to stand for 10 minutes. Add the remaining flour, salt, egg and remaining water and use a knife to combine the mixture until a dough forms.
Place the mixture onto a lightly floured surface and knead for 1 minute to combine the dough to form a ball. Flatten the dough and dot the butter on top. Fold the dough over the butter and return to the bowl to knead for 3-4 minutes, until the butter is fully incorporated.
Cover and rest for 10 minutes. After 10 minutes, continue to knead the dough for another 3-4 minutes, then place back in the bowl, cover and refrigerate for at least 3 hours, or overnight.
Generously grease a 23cm square or round tin.
Remove the dough from the fridge and place on a lightly floured surface. Knock the dough down to flatten it and form a 25 x 20cm rectangle. Brush with the lightly beaten egg and then sprinkle with cinnamon, sugar and chopped macadamia nuts. Gently press the nut mixture down into the dough.
Roll the dough to form a 25cm long sausage shape and then cut into 8-10 pieces about 2-3 cm thick. Nestle the slices, cut side up, into the prepared tin, cover and stand in a warm place until the dough has doubled in size, about 1 hour.
Preheat oven to 200c.
Place the buns in the oven and bake for 10-15 minutes, until golden. Brush with melted butter to serve.