Place the chopped celeriac in a saucepan and cover with water. Add the bouillon and a pinch of salt and bring to a boil. Simmer until very soft, drain and set aside.
Heat a splash of oil in a frying pan and add the shallots and garlic with a pinch of salt. Fry gently for a few minutes or until soft. Add these to the cooked celeriac along with the non-dairy butter and soya milk before seasoning well. Pureé with a hand blender until smooth and keep warm while you make the rest.
Heat a griddle pan until very hot and brush the tempeh rashers with a little oil. Sear them on all sides until piping hot and lightly caramelised.
Heat another splash of oil in the frying pan and add the wild mushrooms. Cook over high heat, stirring until cooked through. Season well and add the tarragon.
Divide the celeriac between 4 plates or bowls. Top with the tempeh and scatter over the mushrooms. Drizzle over any pan juices before serving. Add rocket or watercress, if you like.
