Heat oil in a non-stick pan.
Chop garlic, add and sauté till it turns light brown. Add onion, stir and sauté on medium heat for a minute.
Add potatoes, stir and sauté for 2-3 minutes.
Finely chop thyme and add, mix well, cover and cook till potatoes turn soft.
Add 2 cups stock, stir to mix, cover and cook for 5-7 minutes.
Mash potatoes with a masher. Add remaining stock and mix well. Add salt and crushed peppercorns, mix well, cover and cook for 5-10 minutes.
Add cheddar cheese and mix well. Simmer till cheese melts.
Cut mozzarella cheese into small cubes and add, mix well and bring to a boil.
Garnish with parsley sprig and serve hot.