Peel and trim the parsnips and cut into finger-sized wedges. Trim the baby carrots and halve them.
Heat the oil in a large casserole or deep frying pan, and gently fry the parsnips and carrots for 5 minutes until starting to turn brown at the edges.
Peel and slice the onion, and add to the pan along with the garlic and ginger. Cook for a further 2-3 minutes.
Separate the coriander leaves from their stalks and set aside. Trim and finely chop the stalks and add to the pan.
Roughly chop the tomatoes, and add to the pan along with all their liquid and seeds. Add the curry paste, stir and cook for 3-4 minutes. Season well with salt.
Drain and rinse the lentils and add to the pan along with the coconut milk. Simmer for 4-5 minutes until the sauce is thickened and the parsnips and carrots are cooked through.
Roughly chop the coriander leaves and stir through the curry along with the lemon juice. Taste and adjust seasoning, then serve immediately with rice or naan bread.