Weigh and cube butter, place on plate in freezer.
Place eggs, yeast, sugar and milk into TM bowl and blend 10 sec/speed 5.
Warm 2 min/37°C/speed 1.
Add flour, salt and orange zest and knead 3 min/Interval. Through hole in lid, add cubed butter a little at a time. The finished dough will be sticky and glossy, but quite malleable.
Scrape out onto floured silicone mat and with buttered hands, knead into a smooth ball. Do not be tempted to add flour.
Place into buttered glass bowl, cover tightly with plastic wrap and place in fridge over night (or for at least 12 hours) to rise slowly.
Punch down and divide into four rounds, with a depression in the centre for the custard. Allow to rise in a 40oC oven for as long as it takes to double. (It may take a couple of hours as the dough has to ‘wake up’ after being in the fridge.)
Fill with cooled custard, top with a few blueberries and brush with egg wash before baking for 15-20 minutes in 170oC oven on a bread setting until sounding hollow when tapped on the bottom.
Serve hot or cold.
TO MAKE CUSTARD: Place sugar and orange zest into clean and dry TM bowl and mill 10 sec/speed 10. Add remaining ingredients and cook 8 min/80°C/speed 4. Remove from TM bowl to cool and to prevent the custard from splitting.