The recipe is from Eric Kayser which I have seen on various French bread blogs:

Ingredients

500 g Bread flour

25g sugar

20 g milk powder

75 g 100% hydration starter refreshed

5 g dry instant bakers’yeast

10g salt

250 ml tepid water

75g soft butter

Generous handful of cholocate chips

1 egg yolk to glaze

Method

In a large mixing bowl, dissolve the yeast in the water. Add the starter and mix well.

Add the flour, milk powder, sugar and salt. Knead for 10 minutes.

Add the butter , a little at a time and knead further.

Leave to rest for 15 minutes.

Add cholocate chips to dough, then divide in 4 balls.

Leave to rest for another 15 minutes.

Shape in long baguettes and keep in a baker’s couche or a well floured tea-towel.

With a lame, slash the pain several times.

Leave to proof for 1h30 – 2 hours until doubled in size.

Brush with the egg yolk.

Bake in a hot oven at 220C for 15-20 minutes.

Ideal for breakfast or for us French, as a 4 o'clock "goûter" with 3-4 chocolate pieces !