Fill a pan with water and bring to the boil. Trim and peel the parsnips. Chop them into small chunks. When the water is boiling, slide in the parsnips with a pinch of salt. Pop on a lid, return to the boil, then simmer for 15-20 mins till tender.
Meanwhile, trim the root and top 3cm from the leek and rinse out any grit. Slice into 1cm rounds. Peel and thinly slice the garlic clove. Pull the thyme leaves off their sprigs. Quarter the apples and slice out the cores. Roughly chop the apples.
Trim the kale leaves off their thick cores and roughly chop the leaves. Fill another pan with boiling water and bring to the boil.
Rub the pork escalopes with a generous pinch of salt and pepper. Pour 1 tbsp oil into a large frying pan and bring to a medium-high heat. Add the pork to the pan and fry for 4-5 mins on each side, till golden and cooked through. Transfer to a warm plate, loosely cover with foil and rest while you finish the rest of the dish.
Slide the leek, apples, garlic, thyme and half the butter into the pan you used to cook the pork in. Fry for 5-6 mins, stirring occasionally, till the leek is tender.
When the water is boiling in the second pan, tip in the kale and simmer for 3-4 mins till tender. Drain well.
The parsnips should be cooked by now. Drain them well and return to the pan. Add the remaining butter and a good pinch of salt and pepper. Use a masher to mash till smooth.
Pop the pork escalopes on warm serving plate and top with the buttery apples and leeks. Serve with the mash and kale on the side.