Preparation Inline ingredients (beta)
Cook mode
Step 1 In the bowl of a stand mixer, whisk together butter, milk, yeast, sugar, salt, egg, and yolk until blended. Add flour and use a dough hook to bring the mixture together and knead on low speed for 5 to 7 minutes, until dough is stretchy but soft.
Step 2 Transfer to an oiled bowl, cover tightly with plastic, and set aside for 1 1/2 to 2 hours in a warm spot, until just about doubled. If your kitchen runs cold or things seem to be moving very slowly, heat your oven to 200F for a few minutes and turn it off, and place your bowl in there for the remainder of the rising time.
Step 3 For a longer rise, or to use this tomorrow, you can chill the dough in the fridge. If you are, take it out about 1 1/2 hours before using it so it has time to warm up again before rolling it out.
Step 4 Melt butter in a large sauté pan over medium heat. Add the onions, toss to coat them in butter and cover the pot. Reduce the heat to medium-low and let them slowly steep for 12 to 15 minutes, stirring once or twice.
Step 5 Uncover the pot, raise the heat slightly and stir in salt. Cook onions, stirring every 5 minutes for another 20 to 30 minutes, until golden brown and very tender and sweet. Raise the heat to medium-high and cook the onions until they get a little dark at the edges, about another 5 minutes. Transfer onions to a plate and spread them out so that they cool faster.
Step 6 On a large, well-floured counter, roll out dough until it is about 12 inches wide and as long in length as you can when rolling it thin, likely 10 to 14 inches.
Step 7 Spoon then spread onions over dough in an even layer, then sprinkle onions with 2 teaspoons poppy seeds. Roll the dough up with the filling away from you into a tight coil. Transfer coil to a parchment-lined baking sheet or board to your freezer, just for 5 to 10 minutes.
Step 8 Coat a standard loaf pan with butter or nonstick spray, and line the bottom and two sides with a sling of parchment paper for easier removal.
Step 9 Remove dough from freezer and use a serrated knife to gently cut the log lengthwise into two long strips and lay them next to each other, cut sides up. Lift one side over the next, forming a twist and trying to keep the cut sides facing up. Transfer the twist into your prepared loaf pan.
Step 10 Cover the pan with the same plastic wrap and let it rise another 45 minutes at room temperature.
Step 11 Heat your oven to 350°F.
Step 12 Sprinkle babka with an extra couple pinches of poppy seeds. Bake for 40 to 45 minutes, until a skewer inserted into the center doesn’t feel like it’s hitting sticky/rubbery dough, or the internal temperature is 185°F.
Step 13 If onions get too brown on top, you can put some foil over for the last few minutes. Let cool as long as you can stand in the pan, then cut into thick slices with a serrated knife.
