Well, my version of it, made last night, and very nice it was too.
Melt a good chunk of butter in a pan with some olive oil over a low-ish heat. Add lots of sliced garlic, followed by cubed raw potatoes (about 1cm cubes), salt, black pepper and some dried thyme.
Fry gently until the potatoes are softened and starting to brown, then add some chopped mushrooms. I used older chestnut ones, which meant there was far less liquid than normal generated and gave a really good earthy flavour.
Keep turning occasionally and gently, to stop the potatoes breaking up too much, until the mushrooms are softened and the potatoes are lightly browned all over.