- Dough can be made in a bread machine or as noted here, a stand mixer.
- Place milk, sugar, salt and butter in a small saucepan and heat over low heat until sugar dissolves and butter melts. Let cool until tepid.
- Warm the stainless steel mixer bowl under running hot water. Drain and wipe dry. Add warm water to the bowl and stir in yeast. Stir until yeast dissolves.
- Add milk mixture to yeast and water. With dough hook in place and machine running at low speed, slowly, in small batches, add flour to yeast and milk mixture until all combined. Allow each addition to combine before adding more flour.
- Continue to mix dough until dough ball cleans sides of bowl (or mix until dough ball is smooth and elastic and not sticky). Remove dough from mixer and roll into flattened ball.
- Lightly spray a smooth bowl with cooking spray and place dough ball in bowl. Cover with towel and place in a warm place to rise until doubled in size, about 1 hour.
- While dough is rising, wash and trim root ends and withered stem ends of scallions. Slice into 1/8-inch rounds including green stem. Place sliced onions on a paper towel to dry.
- Remove dough ball to floured surface and punch down. Roll into an 8- x 12-inch rectangle. Lightly brush top surface with water to make slightly sticky. Scatter sliced onions evenly over wetted surface.
- Roll up dough tightly into an 8-inch long cylinder. Wet finger with water and moisten seam. Pinch seam to close. With flats of hands, roll back and forth until dough cylinder evenly lengthens to about 16 inches. Bring ends together. Moisten with water and join ends to make a dough circle. Make a half flip in the dough so that the end-joint is on the bottom and covered. Push ends and sides inward to remove any open spaces.
- Lightly spray a cookie sheet with cooking spray. Place formed loaf on cookie sheet. Cover with a towel and set in a warm space to rise until doubled.
- Bake in a preheated 400°F oven. After 10 minutes, remove and brush with egg and milk mixture. Sprinkle with the poppy seeds - an old spice jar with a shaker lid works well to make a uniform distribution of seeds. Return to oven and bake an additional 20 minutes or until loaf is a nice dark brown.