3/4 cups butter (salted)

1 1/2 cups packed dark brown sugar

3 teaspoons cinnamon

For the egg wash:

1 large egg yolk

1 tablespoon whole milk or cream

Make the dough: Combine the water and yeast in the bowl of a stand mixer, and let stand until the yeast is dissolved. Add the milk, eggs, yolk, sugar, salt and vanilla extract, and whisk until the yolks are completely combined. Add 6 1/4 cups of flour and stir with a stiff spatula until a shaggy, floury dough is formed.

Using a dough hook, knead on medium-low speed until the dough comes together and is no longer floury, about 5 minutes. With the mixer still running, begin adding the butter in 1-tablespoon blobs. Mix until one blob is just barely incorporated before adding the next blob.

When all the butter has been added, continue kneading for another 5 minutes until the dough is silky, elastic and quite jiggly. This won't form a ball like regular dough -- it should bunch around the dough hook and clear the sides of the dough hook, but will still be attached in a sticky dough mass to the bottom of the bowl. Add the extra 1/4 cup of flour as needed if the dough is sticking to the sides of the bowl.

Chill the dough: Transfer the dough to your largest mixing bowl. Cover and let rise for 1 to 1 1/2 hours, until doubled in size. Transfer to the fridge and chill for at least an hour or up to three days. (This makes the dough easier to roll out in the next step.)

...continued