Start the day before you want to bake. Place the flour in a large bowl and add the yeast to one side and the salt and sugar to the other. Mix in the cream and enough water to make a soft, sticky (but not wet) dough. Be aware that it may look a little dry at first but as you begin to knead it it will become stickier so don't add too much water straight away.
Turn the dough out on to an un-floured surface and knead for about 10 minutes until the dough has become elastic and formed a smooth skin, it will be quite sticky at first, but as you knead it will become smooth and supple.
Place the dough in a large bowl, cover, and refrigerate overnight, this will allow it to firm up a little.
The following day, remove the dough from the fridge and allow to sit at room temperature for half an hour or so to warm up a little. Line a baking sheet with greaseproof paper or a silicone liner. Give the dough a very brief knead then divide it into 10 equal pieces.
Shape each piece into a ball then roll them out on a lightly floured surface into a disc about 10cm (4in) wide. Roll the disc up tightly into a batard, roll from either end so that the centre is fatter, pinch the seam tightly to seal and then use your hands to neaten it - it should be fat in the centre and slightly pointed at either end.
Place the shaped rolls seam side down on the baking sheet, making sure that they are well spaced apart. Loosely cover with a clean plastic bag (making sure that it doesn't touch the dough), or with oiled clingfilm. Leave to rise for about 45 minutes until puffy and the dough springs back slowly when you poke it with a finger, if it springs back quickly then it needs a little longer. (They don't rise as much as standard bread dough so don't expect them to quite double in size).
Meanwhile heat the oven to 190C/375F/gas mark 5. Once the buns have risen, gently brush them with egg wash then use a sharp pair of scissors to make about 6 diagonal cuts on the top of each bun in a zig zag pattern.
Bake for 12-15 minutes until golden and the internal temperature registers as 94C/200F (or a skewer inserted into the centre comes out clean). Transfer to a wire rack to cool, store in an airtight container, best served warm.