Bring water to a boil in a pot over medium-high heat. Once it comes to a boil, reduce the flame to medium-low. Add diced potatoes and salt. Then cover the pot with a lid and let it simmer for 15-20 minutes or until the potatoes are tender.
Remove the lid and check if the potatoes are soft. Then take a sieve and drain the potatoes.
Place the sieve over a clean bowl. Then with the back of a ladle, mash the potatoes and pass then through the sieve into the bowl.
Take a small pan and heat it over medium flame. Add butter and allow it to melt. Then add chopped garlic. Fry it for a couple of minutes until they are lightly golden and fragrant.
Add this butter and garlic mixture into the mashed potatoes. Then add grated parmesan cheese, milk, egg yolks and salt (see recipe note). Mix well.
Take a small bowl, add grated cheddar cheese, turmeric powder, paprika powder and milk. Mix well.
Evenly divide the mashed potato mixture into three parts. Add the cheddar cheese mixture into one bowl and give it a good mix. The potato will become orange in colour. To the second bowl, add coriander leaves paste and mix well. This will make the mixture green. We won’t be adding anything to the third bowl and will leave it as it is. This will give us a white/cream colour for the tri-coloured potato swirls.