Put the lentils in a pan of water with the bay leaves and bring to the boil. Continue to boil for 10 mins, then turn down the heat to medium-low and cook for 20 mins more until the lentils are tender.

Meanwhile, heat the oil in a large non-stick pan. Add the onions and fry over a high heat, stirring frequently, until softened. Add the celery, carrots and thyme. Put the lid on, turn down the heat and cook for 10 mins more, stirring now and then until the vegetables are tender.

Drain the lentils and add to the vegetables along with 1 tbsp of the mustard and the vinegar. Measure half the lentils to set aside and use for lunch later in the week (see our lentil salad with beetroot & walnuts recipe). Toss the parsley through the lentil and veg mix.

Meanwhile, spread 1 tsp mustard over the top of the salmon. Wipe a non-stick pan with a drop of oil and cook the salmon skin-side down for about 6 mins. Flip the salmon over and cook for 4 mins more until cooked through. Serve with the lentils, along with a drizzle of balsamic vinegar.