Preheat the oven to 220°c.
Add the chicken, onions, and garlic granules to a large saucepan. Spray with low calorie cooking spray and cook over a medium heat for 5 minutes until the outside of the chicken has coloured and the onion begins to soften.
Add the stock and white wine stock pot to the saucepan. Add the mushrooms and stir.
Simmer over a medium heat for 15 minutes until the stock has reduced and the chicken is cooked through. Once done, remove from the heat.
While the chicken and mushrooms are cooking, add the spaghetti to another saucepan and cover with cold water. Bring to the boil and then reduce the heat to simmer for 10 minutes until the pasta is cooked and softened.
Drain the pasta and add it to the pan with the chicken along with the spinach. Stir to combine until the spinach has wilted slightly.
Add the light cheese spread to the saucepan and stir to coat the pasta and chicken mix. Season with salt and pepper to taste. (Note: it may not need any salt depending on the saltiness of the stock and cheese spread you used).
Pour the mixture into a roasting dish and set aside while you prepare the topping.
In a blender, blitz the bread to make breadcrumbs. Stir in the grated cheese and mustard powder to the breadcrumb mix.
Sprinkle the breadcrumb mix on top of the spaghetti and chicken and spritz the top with low calorie cooking spray. Place into the middle of a hot oven for 20 minutes or until the top is lightly golden.
Remove from the oven and serve.