Place a frying pan on the hob for a few mins (or a large heavy-based casserole dish if you are cooking this on the hob). When warm, drizzle in 1 tbsp olive oil and add the sausages. Fry the sausages for 10 mins, turning them a couple of times till they are browned on most sides.

While the sausages cook, tip the porcini mushrooms into a bowl and cover with warm water. Soak for 2-3 mins, then drain and rinse well under cold water. Tip back into the bowl, cover with more warm water and leave to soak.

Peel and thinly slice the onion and garlic. Trim the celery and cut into 2cm-thick pieces. From this point on, follow the method for either the slow cooker or the hob.

Slow cooker^ Lift the sausages out of the frying pan and pop into a 3½ ltr slow cooker. Trim the carrots and cut them in to 3cm-thick rounds. Peel and cut the potatoes into 2cm cubes. Pop them in the slow cooker with the sausages and add the onion, garlic and celery.

Drain and rinse the lentils. Tip them into the slow cooker. Drain the porcini mushrooms and add them with the chopped tomatoes and bouquet garni. Add a good pinch of salt and pepper. Mix everything together.

Pour in 250ml boiling water and stir. Place a lid on the slow cooker and cook for 6 hrs on medium. For a quicker braise, cook for 2-3 hrs on high or go for a long slow cook for 8-10 hours on low.

Check the potatoes are tender when pierced with a sharp knife. Taste and add more salt and pepper if needed. Divide the sausages and lentils between 4 warm bowls, and drizzle 1 tsp olive oil over each bowlful to serve.

On the hob^ Scoop the sausages out of the casserole dish and pop them in a bowl. Set aside. Add the onion to the casserole dish and cook for 6 mins till softened. Add a splash or 2 of water if the onion sticks a little.

While the onion is cooking, trim the carrots and cut them into 3cm-thick rounds. Peel and cut the potatoes into 2cm cubes. Drain and rinse the lentils.

After the onion has cooked for 6 mins, add the garlic, celery and carrot to the pan. Cook together for 2 mins. Tip the sausages back into the pan along with any resting juices. Then add the potato, lentils and chopped tomatoes. Drain the porcini mushrooms and drop into the casserole with the bouquet garni.

Add plenty of salt and pepper and stir everything together well. Pour in 400ml boiling water and pop on a lid. Bring up to the boil, then reduce the heat and simmer for 30 mins. The potatoes should be just tender after this time and the liquid in the pan reduced.

Taste and add more salt and pepper if needed. Divide the sausages and lentils between 4 warm bowls. Drizzle 1 tsp olive oil over each to serve.