In a large frying pan, heat the oil and butter. Once the butter is foaming gently, add the garlic and fry for a few minutes. Add the porcini and cook for another minute to combine the flavours. Add the fresh mushrooms. Sprinkle with salt and pepper and cook, stirring occasionally, for 5–6 minutes, or until the mushrooms have released their water and are tender and glistening. Add a little of the porcini liquid and let it all bubble for another minute to reduce, then sprinkle with the herbs.