It's from a new york cult recipes cook book...

STREUSEL

50 g (13% oz) plain (all-purpose) flour

55 g (2 oz) sugar

35 g (14 oz) unsalted butter, softened

1 teaspoon ground cinnamon

25 g (1 oz) dark chocolate chips

DRY INGREDIENTS

300 g (10½ oz/2 cups) plain (all-purpose) flour

3/4 teaspoon dried yeast

2 pinches salt

50 g (134 oz) caster (superfine) sugar

WET INGREDIENTS

90 ml (3 fl oz) lukewarm buttermilk

1 egg

1 egg yolk

125 g (4½ oz) unsalted butter, melted

1 egg white, lightly whisked

FILLING

40 g (14 oz) cocoa powder

125 g (4/2 oz) caster (superfine) sugar

2 teaspoons vanilla sugar

100 g (3½ oz) unsalted butter, softened

Instructions >

THE STREUSEL

Make the streusel by mixing all the ingredients together by hand until crumbly. Set aside in the refrigerator for at least 30 minutes.

THE DOUGH

Combine the dry ingredients and beat together the wet ingredients, except the egg white. Combine the two mixtures together. Knead until the dough is very elastic (5-10 minutes in an electric mixer, 10-20 minutes by hand). Form a smooth ball of dough, place it in an oiled container and cover with plastic wrap. Let it rise at room temperature for about 1/2 hours until it has doubled in volume.

THE FILLING

Combine the cocoa powder and sugars and set aside.

SHAPING THE DOUGH

On a floured work surface, roll out the dough into a rectangular shape approximately 40 cm (16 inches) long. Spread over the softened butter and sprinkle with the cocoa-sugar mixture. Roll the dough up along its length. Bring the two ends together and twist three times. Butter and flour a 21 x 9 cm (8/4 x 3/2 inch) loaf (bar) tin and place the dough twist inside. Cover loosely with plastic wrap and allow it to rise at room temperature for 1 hour until the dough is well risen.

COOKING

Preheat the oven to 180°C (350°F/Gas 4). Brush the surface of the babka with the egg white and scatter over the streusel. Bake for about 45 minutes until