Heat the oil in a saucepan and gently sauté the onion, celery, garlic and carrot until soft but not coloured. Add the lentils and turn them over in the oil and vegetable juices. Throw in the thyme and the bay leaf.
Pour on the stock or water, season lightly, bring to the boil, then turn down the heat and simmer the lentils, uncovered, until they are just tender.
This could take anything from 20 to 35 minutes depending on the age of the lentils. Keep testing them until they have reached the right degree of ‘bite’. All the stock should be absorbed.
Meanwhile, make the vinaigrette by simply mixing everything together. Pick the bay and thyme out of the lentils, then add a good squeeze of lemon, the parsley and 3 tbsp vinaigrette while they are still warm.
Heat a frying-pan and cook the pancetta in the fat that runs out of it. Make sure it gets a good colour all over – you need to start on a high heat – and is cooked right through.
Poach the eggs (you can do two at a time if you use a wide sauté pan), draining them on kitchen paper when you lift them out.
Toss the salad leaves with 2 tbsp dressing and mix gently with the lentils. Divide between four plates, scatter with bacon and top with a poached egg. Drizzle each plateful with a little more dressing and serve.