2 package rapid-rise yeast (about 5 teaspoons)
1 tablespoon sugar
5 cups bread flour
2 teaspoons salt
3 eggs, lightly beaten
8 tablespoons unsalted butter, softened
1 egg yolk
2 tablespoons milk
1 tablespoon poppy seeds
Step 1 Mix yeast, ½ teaspoon sugar, and 1 cup warm water in a 2-cup glass measuring cup. Set aside until foamy, about 5 minutes.
Step 2 Mix remaining sugar, flour, and salt in large bowl of electric mixer; add eggs, butter and yeast mixture. Using dough hook attachment, knead at low speed until smooth and satiny, 6 to 8 minutes.
Step 3 Form dough into a ball and let rise in a large, lightly buttered bowl covered with a damp towel until approximately doubled in size, about 1 hour. Deflate to original size, re-form into a ball, cover, and let rise again until doubled in size.
Step 4 Deflate dough again and turn onto a lightly floured work surface. Press dough into a rough square and cut into 4 equal pieces, preferable with a blunt object to seal in gases (a wooden spatula works well. Let rest for 10 minutes.
Step 5 Roll each portion of dough into an 18-inch rope that is thicker in the middle than at the ends, stretching dough as you roll. Place ropes on a large work surface to form an X and pinch in the center to seal. To finish the braid, follow the illustrated steps.
Step 6 Adjust oven rack to middle position and heat oven to 375 degrees. Place braided dough on a lightly greased cookie sheet; cover with damp cloth and let rise until almost doubled, 30 to 45 minutes. Beat yolk with milk; brush entire loaf with this glaze. Sprinkle with poppy seeds and bake until bread is golden brown and internal temperature registers 190 to 120 degrees, 30 to 40 minutes. Transfer bread to a wire rack to cool.
Step 7 Make four ropes of equal length and lay them out in the shape of a four-pointed star; pinch them together in the center to seal. Think of the points as numbered one to four. Starting with point one fold it directly over the center, so that it lies beside point three. Then fold point three directly over the center, again creating a four-pointed star.
Step 8 Now fold point four directly across the center so that it lies parallel to point two; then fold point two over the center, again creating a four-pointed star. Continue this one-side-to-the-other braiding, making sure to keep the bread upright until all the lengths have been folded. As you work, give the ropes a little slack when our reach the center and braid a little more tightly toward the ends. This will give the baked loaf the characteristic high in the middle shape.
Step 9 Pinch the end pieces firmly together at the top.
Step 10 Lay the finished bread down on its side, let rise, glaze and bake.