Preheat the oven to 200°C. Line a large baking sheet with baking paper.
1. Filling Heat the oil and butter in a large pan and add the rosemary sprigs. Stir-fry over medium heat for a minute or until fragrant. Add the mushrooms and stir-fry for 10-15 minutes or until the mushrooms are done.
2. Add the garlic and stir-fry for another minute. Season with salt, pepper and the lemon zest and juice and stir in. Remove from the heat and spoon into a mixing bowl.