Heat a large frying pan over a high heat and add the olive oil and butter. When the butter is foaming add the mushrooms and garlic and season well with salt and pepper. Cook on high until all moisture released by the mushrooms has evaporated, about 10 minutes. Add the wine, shredded meat, spring onions and sage and cook for a minute longer, and stir well to incorporate. Check seasoning and allow the mix to cool a little before filling the filo parcels.
You will need 4 rectangular sheets of filo pastry in total, one for each parcel. Take the first sheet, use a brush to just coat it with olive oil, then cut it in half down the shortest side and place one piece over the other to form a cross. Place a quarter of the mix in the centre, top with brie and cranberry sauce and gather the sides of the pastry up and pinch them together at the top. Repeat with all four parcels then transfer them to a lined baking sheet and brush all over with olive oil before cooking for 10 minutes, or until crispy and golden brown.
