Baking: Babka with Poppy Seed Filling

BABKA DOUGH
1/2 cup milk (plain soy milk will also work)
3 tablespoons unsalted butter
1/4 cup wrist-temperature water
1 1/4 teaspoons yeast (half a package)
3 tablespoons sugar
1 large egg
1 1/4 teaspoons salt
About 2 1/3 cups bread flour or unbleached all-purpose flour
(Enough to make a soft dough)
Nonstick spray for the bowl, the work surface, and your hands

1. DO THIS AHEAD: Gradually heat the milk in a small saucepan until it becomes very hot but is not yet boiling. Remove the pan from the heat, and add cut in the butter in about 4 or 5 slices. Set aside to cool to wrist temperature, during which time the butter will melt.
2. Place the water in a medium-large bowl, sprinkle in the yeast, and let it stand for about 5 minutes.
3. When the milk mixture has cooled to wrist temperature (and no warmer!), add it to the yeast, along with the sugar and salt. Beat in the egg.
4. Add the flour one cup at a time, beating after the first addition with a large whisk, and after the second with a wooden spoon. At some point you will have to graduate from the spoon to using your hand. Add small amounts of flour to keep your hand from sticking too badly, and m;ix until all the flour is incorporated, and you have a soft dough. It's OK if it's slightly sticky.
5. Lightly spray a clean work surface with nonstick spray. Turn out the dough, and knead it just a few times, pushing it into itself, so it comes together in a smooth ball . If it is too sticky to handle, spray the palms of your hands with a little nonstick spray. The goal is to keep the dough as soft as possible–even a little wet!
6. Clean out and dry the bowl (or use a second clean, dry bowl) and coat the inside surface with nonstick spray. Place the dough in the bowl, and spray the top surface with more nonstick spray. Cover the bowl with a clean tea towel, and put it in a warm place to rise until doubled in bulk.
7. Punch down the dough, and proceed with filling and finishing. You can also refrigerate or freeze the dough at this point, if you don't intend to fill and finish it right away. (Wrap it in a sealed plastic bag.)