Warm 120ml milk and the butter in a small saucepan until melted. Leave to cool to lukewarm.
Combine the flour, sugar, salt and yeast in the bowl of a stand mixer. Make a well in the centre and pour in the egg and warmed milk, then mix until just combined. If it seems a little dry, add an extra 20ml milk. Knead the mixture on a gentle speed using a dough hook for 5-8 mins, or until the dough is smooth and springs back when pressed. If you don’t have a stand mixer, combine everything in a bowl, then knead on a lightly floured surface for 8-10 mins. Shape the dough into a ball and leave to prove in a large, lightly oiled bowl covered with a tea towel for 1 hr-1 hr 30 mins, or until doubled in size.
To make the filling, combine the ingredients and set aside.
Line a large baking sheet with baking parchment. Roll the proved dough out on a lightly floured surface to a 40cm square. Spread the filling evenly over the dough using a palette knife, leaving a 2cm border around the edge. Roll the dough up into a tight log, starting with the end furthest from you – it should measure roughly 40cm in length. Cut the dough log in half lengthways down the middle so you have two long pieces laying beside each other, horizontally, cut-side up. Pinch together at both ends, then pick up the ends and twist the pieces around each other, as though you’re making a rope.
Transfer the loaf to the prepared sheet. Loosely cover and let it prove in a warm place until doubled in size again, about 45 mins-1 hr. Heat the oven to 180C/160C fan/gas 4.
Put the sheet in the centre of the oven and bake for 35-40 mins, covering loosely with foil if it starts to become too dark during baking. When ready, the loaf should be golden and sound hollow when tapped on the bottom. Leave to cool slightly for 15 mins if you’re serving it warm, or leave to cool completely on a wire rack.
To make the tahini butter, mix the ingredients with a pinch of salt using a wooden spoon until combined. To make the icing, mix the sugar with 1 tbsp warm water until smooth, adding more if it’s too thick. Drizzle over the loaf and sprinkle with the sesame seeds, if using. Slice the loaf and serve with the honey & tahini butter. Best eaten the day it’s made.