1. If fresh bread is being used instead of stale, preheat the oven to 130°C and spread the bread cubes out on a baking tray. Place in the oven to dry out for 20 minutes before removing and leaving to cool. Change the oven temperature to 170°C.
2. Place a large frying pan over medium-low heat and add the vegan butter. When melted, add the onion and fresh sage. Fry for a total of around 15 minutes, stirring often, until the onions are starting to brown.
3. Add the celery, garlic, parsley and rosemary. Fry for an extra few minutes until the celery has softened then remove from the heat.
4. In a mixing bowl, combine the bread cubes and cornstarch. Add the cooked onion and herbs mixture then stir to combine. Season the mixture with salt and pepper to taste.
5. If making stuffing balls, pour the hot vegetable stock over the mixture and stir to combine. Cover with a teatowel and leave to soak for 5 minutes. Use your hands to divide the mixture into 10-12 balls and place on a lined baking tray. Place in the oven to bake for 20 minutes.
6. If making a dish of scoopable stuffing, transfer the mixture to an oven-proof dish then pour over the hot vegetable stock. Place in the oven to bake for 20 minutes. Remove from the oven and serve.