The day before, make the brioche (these quantities will make more than you need but it freezes well and lasts for several weeks). Place the kumara, milk, vanilla and cinnamon in a pan and bring to the boil, then simmer until the kumara is cooked. Drain the milk from the pan and pour 150 ml of it into a bowl, together with the kumara and vanilla. Discard the cinnamon and remaining milk, then leave to cool to tepid – any hotter and you’ll kill the yeast. Add the yeast and mash everything. Leave until the yeast bubbles.
Sift the 300 g flour and ¼ teaspoon of salt into a mixing bowl with the sugar, rosemary and orange zest, then add the kumara mix and knead with a dough hook or your hands for 5 minutes until it has all come together. Knead in the egg yolks one at a time until incorporated, then slowly add the butter in 5 batches, until you have a soft dough. If it’s very wet, knead in up to a cup of extra flour until no longer sticky. Place in a bowl, cover with cling film and leave in a warm place until it rises. Once increased in size by about a third, knock the air out of it, re-wrap and place in the fridge for 18–24 hours.
Next day, take it from the fridge, punch it a few times, then bring it back to room temperature. When doubled in size, knock it back again, then place in a 1.5 litre loaf tin lined with baking parchment. Cover loosely with cling film and let it rise until doubled in size.
Preheat the oven to 220°C/gas 7. Brush the top of the loaf with a little milk and place in the oven. Quickly and carefully scatter 100 ml boiling water over the bottom of the oven (it provides helpful steam) and bake for 15 minutes. Turn the oven down to 180°C/gas 4 and bake for a further 20 minutes. Poke a skewer into the centre of the loaf and it should come out clean. Take from the oven, leave to cool for 30 minutes, then tip out.
To poach the pears, place them in a pan with the ginger, maple syrup and rosemary. Add enough cold water to cover by 1 cm, then bring to the boil. Turn to a simmer and cook for 45 minutes, with a cartouche or upturned saucer on top to keep them fully submerged. Let cool in the liquid.