Preheat the oven to 180ºC (160ºC fan/gas 4).
Place the chopped celeriac in a bowl, and drizzle with oil. Toss through the oil until each piece is lightly coated. Place the celeriac on a baking tray and bake in the oven until tender, about 20 minutes.
On a separate baking tray place the shallots and drizzle with oil. Slice the leek lengthways and lay facing up on the same baking tray as the shallots. Drizzle with oil. Place tray in the oven and bake both the shallots and leek until lightly caramelised, about 15 minutes.
Peel the apples, remove the core, and thinly slice. Boil sliced apple in water until tender, drain well, then mash into a puree. Set aside.
Remove the celeriac, leeks and shallots from the oven and allow to cool slightly. Add to a food processor or blender and pulse until a roughly textured puree.
Break up the sliced bread roughly and add to the puree mix. Pulse a few times until the bread is mixed through. Add the apple puree, and pulse 1- 2 times.
Add the chopped chestnuts, sage, rosemary and salt and pulse 1-2 times until mixed through. Remove and add this mixture to a bowl, ready to use to fill the pastry.
Line a baking tray with baking paper, and lay out your pastry sheets next to each other on the tray. Cut into 4, so they are equal lengths and widths.
Starting one cm in from the edge of each pastry sheet, add the filling mixture along the length of the pastry with a spoon, making sure to leave one cm gap at all ends.
Being very careful not to tear the pastry, gently but tightly roll each pastry sheet with filling into a long sausage-shaped strand. Pinch each of the ends and edges to secure the filling, so that the filling does not fall apart when baking.
Now begin to plait your pastry. To start, secure all 4 sausage-shaped strands together at the top, by pinching the dough so they stick together. Starting from left to right start overlapping the strands in a plait, and then left to right. Secure at the end by pinching together and overlapping the strands and tucking them under each other to secure.
Place in the fridge for at least 20 minutes to firm up. Can be made up to this point a day in advance and kept covered in the fridge. Once the plaited pastry is chilled, heat the oven to 180ºC (160ºC fan/gas 4).
Mix the agave with the oil and brush all over the pastry, to prevent it from getting too dry, and also to help give the pastry a nice golden colour. Bake for 40-45 mins until golden brown.
Leave to cool for 5 minutes, then transfer to a serving platter and decorate with fresh herbs, and dried cranberries if you wish.
About the chef
Julie is a Naturopathic Chef, who works with Foodservice, Brands and Retail to help them be more sustainable and profitable. Her core message is centred around promoting ‘Healthy People and Healthy Planet’. She advises on sustainable practices and connects businesses with sustainable supply chains, creates healthy recipes with Nutrition as the main focus, and with a strong spotlight on making the most of British Seasonal food.