1. Preheat the oven to 180°C, gas mark 4. Toss the beef in the seasoned flour mixed with the paprika. Heat the oil in a large saucepan and fry the beef in 2 batches to brown, adding the shallots to the second batch. Return the first batch of meat to the pan and add the wine. Cook for 2-3 minutes to reduce a little.
2. Stir in the Dijon, stock and mushrooms, bring to the boil, then cover and simmer on a low heat for 1 hour 30 minutes, stirring occasionally. Remove the lid and cook for a further 20-30 minutes or until the meat is tender and the sauce has thickened. Allow to cool slightly before transferring to a rectangular ovenproof serving dish.
3. Preheat the oven to 200°C, gas mark 6. Roll out the pastry on a floured surface to about 2cm larger than the dish, trim off the pastry edges and place around the edges of the dish. Brush with a little beaten egg then top with the large piece of pastry, pressing the edges to seal. Make 3 slits in the centre and brush with egg to glaze.
4. Bake for 30 minutes or until golden, and serve with mashed potatoes.
FREEZE AHEAD
Allow the filling to cool completely at the end of step 2. Top with the pastry and brush with egg as above, then freeze. To reheat, defrost completely and cook from step 4.