River Cottage

Cut the tops off the squash and if necessary take a slice off the bottom to give a flat base.  Using a spoon scoop out all the seeds and fibrous matter.

Heat the butter and oil in a frying pan when hot add the leeks, cook gently until the leeks are softened but not colored, season with salt and pepper.  When cooked transfer to a bowl to cool slightly, add the grated cheese,  crème fraiche and mustard; taste and adjust seasoning if necessary.

Scoop the leeks into the squashes and place the lids back on.  Put the squashes into a hot oven for a1 – 1 ½ hours.