First, peel the potatoes and cut them into evenly sized chunks. Place them into a pot of salted water and boil until they become fork tender. Once cooked, drain them thoroughly and allow any excess moisture to evaporate for a few minutes.
Next, mash the potatoes until completely smooth using a potato ricer or potato masher. Add the cornstarch, salt, black pepper, paprika, onion powder, garlic powder, and optional MSG. Mix everything together until a smooth, soft dough forms without any lumps.
Place the potato dough between two sheets of parchment paper and roll it out to approximately ½ cm (¼ inch) thick. Remove the top sheet and cut the dough into nugget shapes using a cookie cutter or knife. Transfer the shaped nuggets onto a parchment-lined tray and freeze them for at least 30 minutes until completely firm.
Meanwhile, whisk together the egg, flour, carbonated water, salt, and black pepper until smooth. Place the breadcrumbs into a separate shallow bowl, ready for coating.
Once the nuggets are frozen, dip each one into the prepared batter, allowing any excess batter to drip off. Then coat each nugget generously with breadcrumbs, gently pressing them so the coating sticks evenly.
Heat the oil to 170–175°C (340–350°F). Carefully fry the nuggets in small batches until they become beautifully golden brown and crispy. Remove them with a slotted spoon and drain on a wire rack or paper towels while you prepare the sauce.
Melt the butter in a saucepan over medium heat. Stir in the salt, black pepper, paprika, onion powder, and garlic powder before adding the flour. Cook for about one minute while stirring continuously. Gradually whisk in the milk until smooth, then allow the sauce to simmer gently. Finally, stir in the grated cheddar cheese until fully melted and creamy.
Arrange the crispy potato nuggets on a serving plate and serve immediately with the warm homemade chili cheese sauce for dipping.