Heat your oven to 200°C/Fan 180°C/Gas 6. Slice your marrow into 4-6 thick rounds and scoop out the seeded middles with a spoon. Arrange snugly in an ovenproof dish and bake for 20 mins.
Peel and finely chop the onion and garlic. Peel and coarsely grate the carrot. Pick the leaves from the marjoram. Finely chop half and set the other half aside. Skin the sausages and scoop out the meat.
Warm 1 tsp oil in a large pan over a medium heat. Add the meat and brown for 2-3 mins, breaking it into small pieces with a spoon. Stir in the carrot, onion and garlic. Chuck in the chopped marjoram, a pinch of chilli flakes and some seasoning. Cook for a few mins, till the veg start to soften.
Tip the chopped tomatoes into the pan. Half fill the tin with water and tip this in too. Stir and bring to the boil. Turn down the heat. Simmer for 10 mins.
Take the marrow barrows out of the oven. Fill each hole with the sausage and tomato sauce. Spoon any extra sauce around the edges. Scatter over 2 tbsp breadcrumbs and season. Return to the oven and roast for 25 mins till golden and bubbling.
Tip the bulgar wheat into a heatproof bowl. Pour over 250 ml boiling water. Cover with a large plate or cling film. Set aside for 20 mins.
Serve a couple of the marrow barrows on each plate with a generous spoonful of sauce. Scatter over the remaining marjoram leaves. Pile the bulgar wheat on the side and tuck in.