Cook onion and ground beef in a large skillet over medium-high heat until beef is browned and crumbled.

Add cabbage and cook until wilted, stirring constantly.

Stir in salt, pepper, and 1 tablespoon of celery seed.

Turn off heat and set aside the filling.

Dissolve sugar and yeast in warm water in a large bowl and let stand for 5 minutes.

Stir in milk, 1/2 teaspoon of salt, and beaten eggs.

Lightly spoon flour into dry measuring cups and level with a knife.

Add flour and the remaining 1 tablespoon of celery seed to the yeast mixture, and stir to form a soft dough.

Turn dough out onto a lightly floured surface.

Knead until smooth and elastic, about 8 minutes.

Place dough in a large bowl coated with cooking spray, turning to coat the top.

Cover and let rise in a warm place, free from drafts, for 1 hour or until doubled in size.

Punch dough down, cover, and let rest for 5 minutes.

Divide dough in half.

Roll each half into a 10 1/2 x 7-inch rectangle on a lightly floured surface.

Cut each rectangle into 6 (3 1/2-inch) squares.

Work with one portion at a time (cover remaining dough to prevent drying) and spoon about 1/4 cup of filling into the center of each square.

Bring 2 opposite corners to the center, pinching points to seal.

Bring the remaining 2 corners to the center, pinching points to seal.

Pinch all four edges together to seal.

Place the bierocks, seam sides down, on a large baking sheet covered with parchment paper.

Cover and let rise for 20 minutes.

Preheat oven to 375 degrees F.

Uncover bierocks.

Bake at 375 degrees for 15 minutes or until browned on the bottom and sound hollow when tapped.

Remove bierocks from pan and cool on wire racks.

Optional: for a bakery-type finish, beat 1 egg white and paint egg wash over the dough prior to baking.

Cool completely and wrap individually in foil for freezing.

Place wrapped bierocks in a heavy-duty zip-top plastic bag; freeze for up to 3 months.

To reheat, thaw in the refrigerator.

Place foil-wrapped bierocks in a preheated 350 degrees oven for 15 minutes.