Heat the milk until lukewarm. Crumble in the yeast and stir until dissolved. Grate the lemon zest.
Separate 3 eggs. Beat the butter with the egg yolks, maple syrup and a pinch of salt until frothy. (Use the egg whites in another recipe.)
Add 1 tbsp lemon zest.
Stir in the yeast milk and flour, alternately, and mix to a soft dough.
Knead the dough on a floured surface. Let to stand in a cool place or in the fridge for 8 hours until doubled in size.
Chop the nuts.
Knead the nuts into the dough and let it prove for 30 minutes.
Divide the dough into 3 parts and shape each one in a 15 inch long rolls.
Weave the rolls into a plait and place on a baking tray lined with baking paper.
Separate the remaining egg. Mix the egg yolk with the remaining milk and brush over the plait to glaze.
Place the plait in the cold oven. Turn the oven to 400°F (350°F fan, gas 6) and bake for 45-50 minutes. Allow to cool.