Creamy broccoli, celeriac and cavolo nero pie

1. Preheat the oven to 200˚C, gas mark 6; line 2 baking trays with parchment. Cut the broccoli into small florets and toss with 1 tbsp oil and the paprika; season. Spread out on 1 tray. Toss ½ the celeriac with 1 tbsp oil, season and spread out on the second tray. Put both trays in the oven and roast for 25 minutes, stirring and swapping the trays over halfway.

2. Meanwhile, heat 2 tbsp oil over a medium heat in a large lidded saucepan. Add the onion, garlic and a pinch of salt and sweat for 2-3 minutes until starting to soften. Add the remaining celeriac, cover and cook over a medium-low heat for 20 minutes, stirring occasionally, until just tender and golden. 

3. Transfer to a blender or food processor with the stock, creamy oat, a grating of nutmeg, the allspice and a grind of black pepper (or add everything to the pan and use a stick blender); whizz until smooth. Season with salt, pepper and ½ the lemon juice. Stir in the parsley stalks, ½ the parsley leaves and the dried cranberries. 

4. Boil a kettle. Evenly spread the roasted vegetables over the base of an ovenproof pie dish (about 1.5 litres in volume) and pour over the sauce. Put the cavolo nero in a colander in the sink and pour over the just-boiled water then drain well; squeeze over a little lemon juice and season. Lay on top of the vegetables in the pie dish. Scatter over the remaining parsley.

5. Unroll the pastry sheet and use to cover the pie (roll it out a little more if needed), dampening the edge of the dish with a little water to help it stick. Trim and crimp the edges and cut a small hole in the centre. Use the pastry off-cuts to decorate the top of the pie, if liked.

6. Bake the pie on a baking tray for 25-30 minutes, until golden. Brush the pastry with the agave nectar, then return to the oven for 5 minutes. Allow to stand for 5 minutes before serving.