Old World Poppy Seed Roll
1 (.25 ounce) package active dry yeast 1 egg, separated - white reserved 1 tablespoon butter, melted 1 teaspoon lemon juice 2 cups all-purpose flour, or more if needed 2 tablespoons white sugar ¼ cup butter ½ cup hot milk ½ cup warm water (100 degrees F/38 degrees C) ½ pound poppy seeds ½ teaspoon salt ¾ cup white sugar