Preheat the oven to 200ºC.
Spray a frying pan with low calorie cooking spray and set on a low-medium heat. Add the mushrooms and garlic and cook for 5 minutes.
In a small jug or mixing bowl combine the cream cheese, water, thyme and garlic granules. Season with salt and pepper and leave to one side.
Add the bread to a food processor and whizz into breadcrumbs. Add the Cheddar and Parmesan cheese to the breadcrumbs and stir to combine.
Once the mushrooms have turned lightly golden and softened, add them to an ovenproof dish. Pour over the cream cheese mixture and stir to coat the mushrooms.
Sprinkle over the breadcrumb mixture and pop in the oven for 10 minutes. The top should be crispy and lightly golden.