Mix flour, salt and pepper in a medium bowl and set aside. Heat 2 tbsp. of the olive oil in a large oven safe skillet. Toss the beef in the flour mixture to coat (I save the remaining flour and add it to the sauce before slow cooking in the oven). Brown the stew beef in batches, so the pan is not crowded, and set aside in a dish.
Add the last tablespoon of olive oil to the skillet and add the onions, garlic and celery, cooking just until soft, about 5 minutes. Add the mushrooms, broth and Guinness (and any remaining flour), ketchup and Worcestershire. Stir in the meat. Add extra broth, just enough to cover the meat mixture if needed. Top with the rosemary. Cover the skillet, place in the oven and cook for 3-4 hours, until sauce is thickened and meat is very tender. Cool and refrigerate overnight.
The next day, preheat the oven to 425° and divide the filling between the individual bowls. Sprinkle the peas over each serving, set aside.
Whisk the egg with the tablespoon of water and set aside. Roll out the puff pastry, on a lightly floured surface, to approx. 1/8 of an inch thick. Cut a square that is about an inch larger than the diameter of your serving dishes. Brush the edges of the pastry square with the egg mixture and place over the meat filling, pressing slightly to adhere to the dish. Brush the entire top of the puff pastry with the egg mixture. Set the pie in the fridge while you cut the others. Repeat the process.
Place the servings on a cookie sheet and bake for 30 minutes, until pastry is puffed and golden. Serve immediately.
Makes 1 deep dish pie or 4 individual 2 cup servings.