lightly toast the nuts, this can be done in a frying pan over medium-low heat for about 5 minutes

chop half of them finely and the other half can be chopped a little bigger, then set aside for later

melt the chocolate, butter, and sugar for the filling over medium heat

once it's melted remove it from the heat and stir in the cocoa powder, let the mixture sit until ready to use, it needs to thicken up

for the dough put the flour in the bowl of a stand mixer, put the yeast on one side of the bowl, the salt on another, and the sugar opposite both of them

mix the milk and eggs together

make a well in the center of the flour and pour in the mix egg mixture

mix with the dough hook on low until the dough hook comes together, 2-3 minutes

slowly add the butter in small pieces, beating well after each addition

once the butter is in the dough turn the mixer up one more notch

keep mixing, through the sticky phase, until you get to a soft silky dough, that's when your dough is done

meanwhile lightly butter a 9x5 loaf pan, line with parchment paper

roll the dough on a lightly floured surface to an 11x16 inch rectangle, make sure the long side is perpendicular to you

spread the filling to within 1/4 inch or so of the edges

sprinkle with the prepared nuts

roll it up from the long side of the dough to make a 16-inch roll of dough

pinch the seam to seal

lay it seam side down on the counter and cut it lengthwise

lay the dough cut side up and pinch the top of the two strands together

then fold one side over the other side, and repeat, keeping the open piece of the dough facing up as much as possible

be sure not to stretch the dough out to far, this is going in a 9x5 loaf pan

once the dough is plaited lay it in the prepared pan

cover with plastic wrap of a proofing bag

set in a warm place until doubled in size

when it's almost done proofing preheat the oven to 395˚F

when it's DONE proofing bake for 15 minutes in the preheated oven

THEN reduce to heat to 345˚F and bake another 15-20 minutes or until a toothpick comes out clean, be aware that you might mistake gooey chocolate filling for the loaf being under baked

while to loaf finishes baking mix the sugar syrup ingredients together in a saucepan over medium heat stirring to dissolve the sugar

once it boils quit stirring, reduce the heat and let cook for 5 more minutes, then let it cool

when the babka is done remove it from the oven to a cooling rack, brush with the cooled sugar syrup

when the babka is cool enough to touch use the parchment paper to remove it from the pan

slice and serve while warm

you can let it cool completely and serve cool as well