For the pithivier:
1. For the puree, peel and thinly slice the two butternuts. Slowly cook in 150g butter until soft, season with salt. Puree the mix in a blender until smooth. Return this puree to a pan and cook slowly until all moisture has evaporated and the mix is as dry as possible.
2. Cool the puree down and add diced butternut, pine nuts, parmesan, sage and mustard fruits. Check seasoning.
3. Take 4 tea cups and line them with cling film. Fill each cup with 120g of mix. Level the mix off flat, fold over the cling film and freeze.
4. Roll out the puff pastry to 3mm thick.
5. Cut out eight discs. For the bottom cut 100mm diameter and for the tops 130mm.
6. Take out the butternut fillings from the freezer, remove from cups, remove cling film. Place each filling (flat side down, domed side facing up) onto bottom pastry disc.
7. Crack one egg into a bowl and add three yolks, mix with a fork.
8. Brush egg mix round edge of bottom pastry disc. Put the pastry top onto the butternut mix and mould with your hands down to the base squeezing out the air as you go. Attach the two discs together where they meet at the egg mix.
9. Put the pithiviers in the fridge for one hour then cut out round the base leaving a 5mm lip. Make a small hole at the top to release the steam when cooking. With a pastry brush, cover with egg mix. Put in fridge for one hour and the cover with egg mix again. Store in fridge to set for one hour.
10. Pre-heat a fan oven to 200 degrees Celsius. Cook pithiviers for 7 minutes, rotate them 180 degrees and cook for 4 minutes more.
For the mushroom bisque:
1. Slice button mushrooms very thin.
2. Melt butter in a pan and fry mushrooms until golden brown.
3. Drain off butter and return mushrooms to a saucepan.
4. Just cover with water and a pinch of salt.
5. Bring to the boil, simmer for one minute.
6. Remove from heat and cling film pan.
7. When cool, put pan in fridge overnight.
8. Next day, remove cling film and boil.
9. Pass liquid through fine strainer and pour in to a fresh saucepan.
10. Boil and reduce mushroom stock all the way down to syrup.
11. Add cream and re-boil.
12. Add lemon juice and check seasoning
For the Scorched Leeks:
1. Boil the whole leeks gently in salted water until soft.
2. Cool down and dry on a cloth.
3. Slice leeks into 2cm discs.
4. In a hot frying pan, fry the leeks on either cut side until coloured heavily. Season with salt.
To Finish:
In a bowl, place 9 pieces of leek. Place the pithivier on top then pour around some of the hot mushroom bisque.