Cut the mushrooms into pieces and add to a dry pan on medium heat. Saute. Remove the pan from the heat and let cool. Now Heat olive oil and butter in the same saucepan.
Chop onions. Saute. Cook the chopped leek until tender. Sauté minced garlic. Cook until thyme is fragrant. Now Cook the chicken until it is fully cooked. Mix in the double cream.
Mix in saute mushrooms. Turn heat off. Bake the filling in a baking pan and top with mozzarella cheese and cheddar cheese. Bake for about 20 minutes or until the top is golden brown. Serve immediately