Preheat oven to 350°F. Line a baking sheet with parchment paper. Dust lightly with cornmeal.

In a large skillet, heat olive oil over medium-high heat. Add yellow onions and flour, saute for about 5 minutes.

Add in the ground beef and brown, stirring frequently, about 5 minutes.

Add the butternut squash and diced potatoes, stirring and cook for 5 - 10 minutes. Season with the Worcestershire sauce, nutmeg, salt, and beef broth, mixing well. Reduce the heat to simmer and cook for 15 - 20 minutes, with the lid askew, cooking until most of the broth is cooked down and vegetables are tender.

On a lightly flour-dusted surface, roll out the frozen puff pastry sheets one at a time until each sheet is slightly thinner than a 1/4 inch thick. Cut each sheet into 4 squares. Fill each square with 1/4 cup of beef and potato filling, leaving 1/4 inch border, crimp edges to seal. Brush the top of the pasties with the beaten egg wash and dust the tops lightly with cornmeal.

Bake in a preheated 350°F oven until the puff pastry is golden brown. Serve immediately.