Heat the oven to 180C/350F/Gas4. Slice the lid off the squash a quarter of the way down its flesh. Set the top aside and scoop out the seeds. Place the mustard, thyme and crème fraîche or cream into a bowl, season with salt and pepper and stir well to combine. Spoon half into the base of the squash, followed by a layer of Gruyère.

Trim the crusts off the bread and tear into one-inch pieces. Layer the bread on top and then pour over the remaining cream. Return the lid to the squash, place on a baking tray and bake on the middle shelf of the oven for one hour. Remove and allow to cool slightly, then serve as it is or spoon on to plates, scraping all the squash out as you do so. Serve with salad.