Sweat the shallot in a little vegetable oil until soft, then mix into all the other filling ingredients. Using a large sheet of cling film form the mixture into a long sausage shape. Chill it in the fridge until ready to use.
Put the flour, salt and butter into a food processor and roughly pulse. Make sure you don’t turn it into a fine breadcrumb-type mix, you want big lumps of butter. Add just enough water to just bring it together, the pastry should be fairly dry. Flatten your dough and shape into a rough rectangle and chill it in the fridge for a few minutes to firm up.
Roll the pastry into a rectangle a couple of centimetres thick. Fold the top third down to the centre, then the bottom third up and over that. Give the dough a quarter turn (to the left or right) and roll it out again to three times the length. Fold as before, and cover with cling film. You can now store it in the fridge or freezer until required.
Roll out your pastry to a thickness of about 5mm. Trim to create a straight edge. Unwrap your sausage and place on the pastry along the straight edge. Roll over in the pastry and cut along the length of the sausage roll. Place on a parchment-lined baking tray then brush with egg yolk.
For an extra glaze and flavour boost, while still warm brush with an equal mix of black treacle and Marmite.
Using a serrated knife, slice into sausage rolls of whatever size you fancy.
We serve these with Madeira sauce at The West House, but they’re great with your favourite gravy or with a dollop of HP sauce.