Prepare the Poppy Seed Filling Place 1 lb dry poppy seeds in a large pot and cover generously with water. Bring to a boil, then remove from heat and cover. Let soften in water (refrigerate if soaking up to 12 hours). Drain through a cheesecloth-lined fine-mesh strainer, pressing and allowing to drain thoroughly to extract excess water. Grind drained seeds in batches in a food processor or poppy seed grinder until finely broken down and moist-looking. Mix ground seeds with condensed milk, 2 tbsp flour, and 1 egg white until evenly combined and thick. Refrigerate until cold.

Mix & Knead the Dough Combine lukewarm milk, instant yeast, sugar, beaten eggs, and bread flour in a stand mixer. Mix on low speed for 3–4 minutes until no dry flour remains. Add salt and mix for 2 minutes more. Add softened butter gradually, allowing it to incorporate. Continue kneading for 10–15 minutes until the dough is smooth, elastic, stretchy, and slightly tacky.

First Rise & Overnight Option Transfer to a lightly greased container, cover, and let rise at 76–80°F (24–28°C) for 1–1.5 hours until noticeably puffy (give 1 set of stretch-and-folds during the first hour if needed). Refrigerate covered for at least 2 hours or overnight to firm up the butter for easier rolling.

Two Ways to Shape Option 1 (Classic Spiral Rolls): Roll cold dough into a thin rectangle (~¼ inch / 5 mm thick). Spread a manageable layer of cold poppy seed filling, leaving a narrow border. Roll into a snug log, pinch seam closed, and slice into 1–1.5 inch (3–4 cm) pieces using a sharp knife or dental floss. Option 2 (Extra-Filled Rolls): Pre-shape a portion of cold filling into a tight log on plastic wrap and freeze until firm. Roll dough thin, spread filling over one half, and fold the plain half over. Place frozen filling log along one edge and roll dough tightly around it into a cylinder before slicing into rounds.

Final Proof & Bake Arrange rolls on a parchment-lined tray (or in individual round baking rings). Cover loosely and proof at 76–80°F (24–28°C) for 1.5–2 hours until puffy and airy. Preheat oven to 350°F (175°C). Brush tops with optional egg wash. Bake for 28–30 minutes until golden and the dough is fully baked through.

Sweet Syrup Finish Boil ½ cup sugar and ½ cup water over medium heat until bubbly and sugar dissolves. Brush warm rolls generously with sweet syrup for a glossy finish. Serve warm or at room temperature with cold milk!