In a large pan, heat 3 tablespoons of the olive oil and gently fry the onion for 3 minutes. Add the celery and garlic and cook for 2 minutes, then turn up the heat and add the red pepper. Fry for 2 to 3 minutes, stirring, then add the harissa paste and stir well.

Add the lentils and stir to coat. Pour in the passata and the stock, stir and simmer for about 10 minutes.

Fry the sausages in the remaining oil for a few minutes until browned. Remove from the pan, reserving a little oil, then cool. Cut on the diagonal into 2.5cm (1 in) chunks and add to the soup.

Trim the lamb. Fry the steaks for 2 minutes on each side, then cut into 1 cm (1/2 in) slices. Serve the soup topped with the sausage chunks and lamb slices and garnish with the mint sprigs.