Begin by re-hydrating the dried mushrooms in hot water. This will take roughly 10-15 minutes.
In the meantime, dice the mushroom and add to a hot pan with a splash of olive oil and a large pinch of salt.
Saute the onions until they are just translucent.
Roughly chop the mushrooms and add to the pan. Cook for 5 minutes or until softened.
Next, add the garlic (crushed) and the pre-cooked chestnuts (also roughly chopped). Cook these with the onion and mushrooms for a further 2-3 minutes.
Remove the leaves from the sprigs of rosemary and thyme and add to the pan for a few brief minutes until they are releasing their aroma.
Take the pan off the heat and let it cool for a few moments before adding to the blender along with the dried mushrooms that have now been re-hydrated. Do not add the liquid to the blender at this stage.
Turn the blender on to its lowest setting and let it run for a few minutes until a paste begins to form. Add the red wine vinegar and a little bit of the re-hydration liquid if it is struggling to blend. Avoid adding too much or your pâté will be too wet.
Gradually increase the speed on your blender until the desired texture has been achieved.
While the pâté is still hot, spoon it into your sterilised jar(s) or ramekins.
Melt the non-dairy butter and then pour a thin layer over the pâté.
Seal the jar(s) or cover the ramekins and leave them to cool completely before storing in the fridge until ready to serve.