Preheat the oven to 200°C (180°C fan, gas 6).
Wash the celery.
Peel the carrots.
Wash the leeks and cut off the green.
Wash the celeriac.
Wash the parsley and shake dry.
Cut the loaves into slices, then into small cubes.
Cut 2-3 sticks of celery into fine strips, then dice as finely as possible. Very finely dice 1-2 carrots. Saute both in the butter for 5 minutes.
Chop the remaining carrots, celery, leeks and celeriac.
Finely chop the parsley.
Place the bread cubes, parsley and finely diced vegetables in a bowl. Grate in some lemon zest and mix well.
Add the eggs and egg yolks to the bread mixture.
Mix everything well. Add some crumbs, if the mixture is too liquid. Season with salt, pepper and nutmeg.
Stuff the breadcrumb mix into the meat pocket.
Secure with kitchen string.
Season the meat with salt and pepper. Place in a oiled roasting tin and roast in the oven for 20 minutes, turning occasionally.
Add the vegetables to the roasting tin, turn the meat and place on top. Pour in the wine and some stock and roast for 2 hours and 10 minutes. Add more broth if necessary and baste with the meat juices regularly.
Remove the meat from the oven, cover and leave to rest. Sieve the pan juices and thicken with cornflour if necessary. Carve the meat and serve with a salad.