Use the softened tablespoon of butter to grease the bottom and the sides of a 12-inch cast-iron skillet. If you don’t have a cast-iron skillet, you can use any other heavy skillet or just simply grease a large baking sheet with the butter.
In the bowl of a stand mixer with a dough hook, stir together the warm water and the yeast. Add the sugar. Let the bowl sit undisturbed for about 15 minutes to allow the yeast to develop.
Crack the eggs into a small bowl and beat them lightly. Add the oil and the eggs to the yeast and water mixture. Stir the ingredients together.
Add 3 ½ cups flour to the mixture and stir the dough with a wooden spoon until the dough is smooth.
Cover the bowl with a clean dish towel and place it in a warm place to rise for about an hour or until it is doubled in size.
When the dough has risen, punch it down and put it on the mixer stand with the dough hook attached. Use the dough hook to knead the dough for 3 to 5 minutes. The dough should be smooth and shiny and pull away from the sides of the bowl. Add a bit of flour if it is too sticky.
When the dough is fully kneaded, divide it in half.
Split each half of the dough into three pieces that are roughly equal in size. On a lightly floured surface, roll these pieces into ropes that are 12 to 18 inches long. Lay three of the ropes side by side.
Crisscross the centers of the ropes.
Starting at the center of the ropes, braid them together until you reach the ends.
Repeat on both ends with both sets of ropes. When finished, you will have two separate braided loaves of bread.
Place each loaf in the prepared skillet, curving it around the outside of the pan to create a wreath. Stick the ends of the loaves together by pressing each rope together.
Spread a kitchen towel over the top of the skillet and let the bread rise until it is nearly doubled in size, about 30 or 40 minutes. While the bread is rising, preheat your oven to 350 degrees.
After the bread has risen, in a small bowl, beat the egg for the bread glaze and then brush the loaf of bread with the egg. Sprinkle the loaf with poppy seeds.
Bake the bread in the preheated oven for about 20 minutes or until it is golden brown. Cover the bread with a tented sheet of aluminum foil to prevent its over-browning. Return it to the oven for 15 or 20 more minutes or until it sounds hollow when lightly tapped.
Let the bread cool in the pan for about 20 minutes and then transfer to a wire rack to fully cool.
Slice and serve.