Source for the base recipe (uses a chocolate glaze): http://www.foodandwine.com/recipes/chocolate-babka

Dough:
4 cups all-purpose flour
1/3 cup sugar
2 teaspoons salt
1 cup whole milk, warmed
2.25 tsp (or one packet) yeast
1 large egg plus 1 large egg yolk
1 stick plus 2 tablespoons unsalted butter, at room temperature

1. Mix the milk and yeast, let sit for a few minutes
2. Mix in the eggs
3. Mix in the dry ingredients until a dough forms
4. Mix in the butter, which takes a little bit — even with a dough hook. Scraping down the sides is a must.
5. Cover in saran wrap, let sit for two hours, then refrigerate overnight
6. Pull out of the fridge and let sit for an hour or two before baking (maybe not necessary)

Filling:
12 oz chocolate
1.5 sticks butter – both melted together
optional: poppy seeds, nigella seeds, sesame seeds, black pepper, spices (probably nuts, though I haven’t tried that)

Assembly:
1. Split the dough, roll each into a rectangle that’s about a foot wide and however long it can be (probably 1.5ft?)
2. Spread the chocolate (and other fillings) on the inside, then roll it up, pinching the ends. Repeat with the second half of the dough.
3. Place the logs in the freezer for ~10 minutes
4. Slice lengthwise, then put each in a parchment lined loaf pan, twisting the two while they face up twice.
5. Let rise until puffy (~2 hours), and bake at 275 for 30-40 minutes (depending on dough temp etc)

Loaf pan size: 9×5 makes a flatter loaf, 8×4 makes a slightly overflowing loaf

Glaze:
6tbsp sugar
1/3c water or whiskey (or both)
1. Cook together until a thin syrup forms
2. Once the loaves are pulled from the over, brush glaze over (it’ll seem like a lot, but the loaves can hold quite a bit)