I really call these chocolate buns, which sounds a bit more sensible, but they are a lunchbox-friendly version of pain au chocolate - made as a sandwich alternative for school lunches.
They are based on a fruit bun recipe, but with a square of chocolate instead of the fruit.
Put flour in a large bowl and rub in the butter. Stir in salt, cinnamon and sugar, then mix in the water and milk. Make a soft dough and knead for a few minutes, then leave, in the covered bowl, to double in size for an hour or two in a warm place.
When risen, punch down dough and divide into eight or so pieces. Give each piece a quick knead in your hands then seal a square of chocolate in the middle of each piece. Put on baking sheet, join side down.
Leave buns covered, to rise, while you heat oven to 200 C, then cook for around 20 minutes until tops are browned and bottoms sound hollow when tapped.
Good when still warm from the oven, as chocolate is soft and melted, but still nice when cool.
450 g bread flour
25 g butter
1 tsp salt
30 g caster sugar
2 tsp ground cinnamon
2 tsp instant yeast
150 ml lukewarm water
150 ml milk, lukewarm
chocolate squares, 1 for each bun (I used cooking chocolate, but normal would probably be good too)