Stuffed shoulder of lamb

Brush the shoulder of lamb with olive oil, season with freshly ground black pepper to taste and sprinkle with lemon juice.
Leave to marinate for four hours or overnight.
To make the stuffing, heat 15 ml of the butter in a pan and cook the onion over a low heat until soft. Set aside.
Wash the spinach, give it a shake and cook it in the water left clinging to the leaves, until tender.
Drain the spinach well, using a saucer to press out any excess water.
Chop it finely and add the remaining butter.
In a mixing bowl, combine the cooked onion, spinach, sausage meat, herbs and egg with salt and freshly ground black pepper to taste.
Mix together well, then spread the stuffing over the meat up to one centimetre away from the edges.
Roll up the meat and tie with string at 1 cm intervals.
Dust the roll with flour.
Heat the olive oil and butter in a roasting pan and add the meat.
Turn to seal the meat all over.
Place the roasting pan in a preheated oven and roast at 160 °C for 1 1/2 to 2 hours. Baste frequently.
Lift the meat from the roasting pan and allow it to rest in a warm place before carving.
Pour off excess fat, leaving just enough to absorb the flour.
Mix together and scrape all the brown bits from the bottom of the pan.
Add the tomato purée and stock, and stir until the gravy boils.
Season to taste and serve with the meat, together with roast potatoes and green vegetables.