Pre-heat the oven to 180°C (fan)/200°C/gas mark 6. Grease a 20cm ring tin or plain savarin mould. (You could use a standard loaf tin but you may need to adjust the cooking time.)
Peel and chop 400g parsnips and steam (or boil) them until soft. Mash.
While the parsnips are cooking grind 2 tbsp chia seeds to a powder in a spice grinder or a pestle and mortar. Add 6 tbsp water and stir until you have a gloopy paste that's a bit like glue. Set aside.
Heat 1 tbsp olive oil in a frying pan and sauté a chopped onion until soft stirring often. Add 2 cloves crushed garlic, 6 chopped sage leaves and 1/4 tsp nutmeg and continue cooking for a moment or two.
Stir through 180g chopped chestnuts, 125g ground almonds, a small handful of chopped parsley and your chia paste and mashed parsnips. Warm through and season with salt and pepper to taste.
Transfer to your prepared tin and bake for 20 minutes. After 10 minutes check and cover with foil if it's getting too brown.
Allow to cool in the tin for five minutes then pop a plate over the top, carefully invert and the wreath should slide out. If it's a little stubborn turn it back over, run a knife around the sides and try again.
If making the oaty topping, just before serving heat the olive oil in a small frying pan, add the sage leaves and fry until going crispy. Add the breadcrumbs and oats and stir well. Cook for a couple of minutes then sprinkle over the top.
Serve with roast potatoes, veggies and a vegan onion gravy.