Heat your oven to 200°C/Fan 180°C/Gas 6. Trim the parsnips and cut into quarters lengthways. Place on a baking tray. Whisk 2 tsp honey with 1 tsp oil. Drizzle over the parsnips and season.
Wrap a garlic clove in a square of foil and nestle next to the parsnips. Slide into the oven and roast for 30 mins till the parsnips are soft and golden. Flip the parsnips over halfway through cooking.
Toast 1 tbsp sunflower seeds in a dry frying pan over a medium heat for 2 mins till golden and nutty smelling. Tip into a food processor. Strip the kale leaves from the middle cores. Add to the processor. Blitz till they form a paste. Zest and juice in half the lemon. Season. Slowly trickle in 2-4 tbsp cold water till you get a pesto-like paste.
Peel and finely chop the onion. Finely chop the carrot and celery. Peel and grate or crush the remaining garlic cloves. Finely chop the rosemary leaves.
Heat 1 tsp oil in a pan. Add the chopped onion, carrot and celery. Cook for 6 mins over a medium heat till softened. Add the grated or crushed garlic and cook for 1 min. Add the rosemary and cook for 1 min.
Drain and rinse the lentils. Add them to the pan and warm through for 5 mins. Unwrap the roast garlic clove and press down on it with a fork to squeeze it from its skin. Stir the garlic into the kale pesto. Add more lemon juice if desired.
Pile the lentils onto warmed plates. Top with the honeyed parsnips. Serve with the kale pesto and any remaining lemon sliced into wedges for squeezing.