Place potatoes into a large pot with enough water. Cover and bring to a boil. Reduce heat to medium-low and simmer until tender, about 20-25 minutes; drain.
Generously butter 4 (9cm) ramekins and dust bottom and sides thoroughly with breadcrumbs, making sure breadcrumbs are covering all the butter inside the dish. Tap out the excess sugar. Set aside.
Preheat your oven to 220℃ (425℉).
Place the boiled and peeled potatoes in a large bowl and mash them. Add the grated cheddar, parmesan, salt, pepper, garlic powder, chili powder, melted butter, milk, egg yolks and chopped coriander. Mix everything using a spatula until well combined.
Now, using an electric mixer beat egg whites at medium speed until the mixture is fluffy and medium peaks form. Gently fold the egg whites into the potato mixture.
Fill the prepared ramekins with potato mixture. Rub your thumb around the inside of the rim to create about a ¼-inch space between the dish and the soufflé mixture. This will help the soufflé to rise straight.
Transfer ramekins into a baking tray and bake until the soufflés are puffed and and the tops are touched with brown, about 20 minutes. Remove from the oven, sprinkle with a little spring onions and serve immediately.