In a small bowl, mix together the warm water and instant yeast.
In a stand bread mixer bowl, add in the pumpkin puree, two of the eggs, brown sugar, spices and salt. Mix together
Add in the flour and the yeast mixture.
Start the mixer and add in the butter, a tablespoon at time, waiting till each tablespoon is incorporated before adding the next.
Mix on high for at least 15 minutes. The mixture will start off very sticky but keep mixing until it forms a ball and there is no more dough stuck to the sides of the bowl. When touched the dough will still be sticky but will be quite elastic and stretchy.
Place in a greased bowl, covered with a damp tea towel and let it rise in a warm place for an hour until doubled in size.
Punch down the dough and tip on a floured bench. Shape into 12 balls and place in a greased or line glass tray. Alternatively shape into two loaves and place into two lined loaf tins.
Cover with a tea towel and leave to double in size. Once doubled, either move onto the baking step or transfer to the refrigerator to ferment overnight. (It can be kept in the fridge for up to 16 hours.)
Heat your oven to 180 degrees Celsius. Mix the egg yolk with 1 tablespoon water and brush over the dough.
Bake for 35 minutes until the tops are a shiny dark brown. Let cool before removing them from the tray by pulling them apart.