Method

1. Preheat the oven to 180C/350F/Gas 4. Line a large roasting tin with foil, leaving the ends hanging over the edges of the tin.

2. Bring a large pan of water to the boil – the pan needs to be large enough to hold the marrow halves. Season the water lightly with salt.

3. Scoop the seeds and stringy pulp from the marrow halves using a spoon, and discard. Scoop about 120g/4½oz of the flesh from the inside of the marrow, creating a large hollow, and put to one side.

4. Carefully lower the hollowed marrow halves into the pan of boiling water, immediately turn the heat off and leave them sitting in the hot water until you are ready to use them.

5. Crush the garlic and fresh thyme in a pestle and mortar and add salt and freshly ground pepper to taste. Heat the olive oil in a pan, add the onions, followed by the garlic and thyme, and then fry until soft. Add the beef mince and cook for about 10 minutes, stirring regularly until browned.

6. If using fresh tomatoes, prepare them whilst the beef is browning: place the tomatoes in a bowl. Pour over boiling water, and leave for 30 seconds. Remove with a slotted spoon, run under cold water, and peel the skin from the flesh. Discard the skin, and chop the peeled tomatoes roughly.

7. Add the tomato purée and sun-dried tomato paste (or chopped sun-dried tomatoes if using) to the browned beef mince, and cook for another 5 minutes. Chop the reserved flesh from the marrow and stir it into the sauce, stir in the chopped tomatoes, and parsley and cook for a further 10 minutes, stirring occasionally.

8. Take the sauce off the heat and let it cool briefly before stirring in the eggs (if the eggs are stirred in too soon they will scramble).

9. Add half of the parmesan and pecorino to the pan and stir until well combined.

10. Carefully remove the 2 halves of marrow from the hot water, draining any water from the centre, and place them in the baking tin. Spoon the sauce mixture into each of the marrow halves until they are full. Gently push the halves together, and brush the skin with olive oil. Sprinkle the remaining half of the grated cheeses over the top of the marrow. Wrap the sides of the foil around the marrow to hold it together, leaving a small gap at the top.

11. Bake in the preheated oven for about 45 minutes. After 45 minutes, increase the temperature to 200C/400F/Gas 6, open out the foil and cook for another 5 minutes so the grated cheese can brown and become crispy. Remove from the oven, and allow to rest for 10 minutes.

12. To serve, slice the marrow into rings, and sprinkle with extra parmesan and parsley to serve, if you like.