Preheat the oven to 200C/400F.
Add the olive oil to a nonstick wok or extra large pan (you need space to add your bread cubes) over a medium high heat. Once warm, add the finely chopped fennel, carrot and sage and cook until the vegetables start to lose their form.
After about 10-15 minutes, the vegetables should be caramelised and small. They should have a golden brown colour. Once they do, boil the kettle.
Pour the boiling water over the stock cubes miso paste and nutritional yeast in a small bowl. Set aside to dissolve.
If you're using it, add the finely chopped apple, and cook for a couple of minutes to combine. Next, pour over the liquid mixture, scraping all the leftover flavouring into the pan.
Cook the liquid down for 3-5 minutes over a gentle heat, before adding the bread chunks. Cook just until all the bread is moist and covered in flavours.
Transfer the mixture to a baking pan, and cook for 20-30 minutes, or until golden.