Add the garlic, mustard, cheese, cream, breadcrumbs, and parsley to a bowl, and mix well until fully combined. Season with salt.
Lightly drizzle the mushrooms with olive oil and roast at 180°C for about 15 minutes.
Remove from the oven and let the mushrooms cool for a few minutes till they can be handled. Fill each mushroom with the cheese and garlic mix, top with a little pat of butter, and put back in the oven. Grill the mushrooms until they're golden and and bubbling.
Serve with a garnish of chopped parsley and a sprinkling of pepper.
