Children’s novel I read in the 90s about two kids who get lost in the woods or “brush”, they find a large abandoned Victorian-looking house beside a lake to take shelter in. They survive off the overgrown garden with rhubarb and raspberries, and fishing from the lake. Their large black shaggy dog, always has hair falling in their eyes (possibly named Sadie?) ends up finding them and returning them to safety.
The book’s cover was yellow/beige, had an oval frame with the shaggy dog’s head extending out like a photograph. Many many thanks for your help!!