Follow the package directions for defrosting the puff pastry.
While the pastry defrosts, heat the broth in a large pot over medium heat. Once the broth is hot, add pearl onions, and cook 2 minutes. Add potatoes, carrots, and sausage, and cook 10 minutes. Add peas, and remove from heat.
Using a slotted spoon, transfer the veggies and sausage to ovenproof soup ramekins (bowls). Reserve the broth in the stock pot.
In a medium pan, melt butter, and add the flour. Cook 3 minutes, or until the flour mixture starts to brown. Slowly whisk in broth, and cook until the sauce thickens, about 2-3 minutes. Add cream, and cook an additional minute, or until heated through. Taste for seasoning, adding salt and pepper to taste. Pour sauce over the veggies in the soup ramekins.
Roll out the pasty, cut to fit over each bowl, and crimp the edges to the bowl. Cut a vent in the center with a sharp knife. Brush the puff pastry with the beaten egg white. Place the bowls on a large cookie sheet to catch any drips that might spill over during baking.
If you have additional puff pasty, cut it into strips, and bake it on a separate cookie sheet with the pot pies to make puff pastry straws.
Bake pot pies in 425° F for 10 minutes. Without taking the pot pies out of the oven, lower the heat to 350° F and bake 20-25 minutes. Serve hot.
Pot pies can be made ahead and reheated.Sometimes when I'm feeling lazy, I just make the filling and serve it as a soup or stew. Maybe with some sourdough bread and a green salad on the side. If you want to do this, just cook in step 2 until the potatoes are fork tender, then add the peas. Continue on with the recipe skipping the puff pastry and the baking.