Preheat oven to 200°C. Season the beef generously with salt and pepper, then drizzle with half the oil. Sear in a pan set over a high heat for 10 minutes, until very well browned. Set aside.
Add the celery, onions, garlic and Herbes de Provence to the pan with the remaining oil and cook for 5 minutes, until softened. Sprinkle with the flour, cook briefly, then return the beef with the stock and tomato paste. Simmer for 2 hours, until the beef is tender. Set aside to cool completely.
Cut eight discs of puff pastry. Line into four individual pie dishes, then spoon in the filling. Top with the remaining pastry, brush with egg, and sprinkle with pepper. Bake for 40 minutes, until the pastry is crisp and well-browned.