Bring a large pan of water to the boil. Trim the ends of the turnips and any tough blemishes. Slice into 1cm thick rounds. Pop the slices into the pan and simmer for 6-8 minutes until they start to soften but are not overcooked. Turn off the heat and drain. Leave to cool slightly.
Heat a couple of tablespoons of water in the bottom of a medium fryin pan and add the sliced onions with a pinch of salt. Sauté on a medium heat for 5 minutes, adding more water if needed. Add the garlic and thyme to the pan and cook for another minute then add the turnip greens (or kale) to the pan and cook with the lid on for a couple of minutes. Turn off the heat.
Blend the sauce ingredients together in a small blender pot or in a bowl with a hand blender.
Pre-heat the oven to 180ºC. Lightly spray the bottom and sides of an oven proof dish to prevent sticking (optional if oil-free, just be aware of extra washing up!).
Layer half the turnip slices over the base of the dish. Cover with the onion and greens mix. Season with salt and pepper and add a little more thyme if desired. Finish with a second layer of turnip slices and season again.
Poor the sauce over the layered turnip and move around to make sure it covers all the veg. Pop in the oven and bake for 15-18 minutes until the turnips are super soft and the top is lightly browned. Remove from the oven and served immediately, or leave to cool and warm up in the oven later.
