Add the potatoes to a large sauce pan. Add enough cold water to the pan to cover the potatoes. Bring to a boil and cook until tender, about 15-20 minutes. Drain. Add the potatoes to a large bowl and mash with the milk and butter. Stir in the scallions and dill and season with salt to taste.
Meanwhile, sauté the cabbage. Heat the olive oil in a pan over medium heat. Add the cabbage and cook, stirring occasionally, until softened; about 10 minutes. Add the garlic and cook for 1-2 more minutes. Season with salt to taste. Stir the cabbage into the mashed potatoes and transfer to the refrigerator to chill for at least 1 hour or preferably overnight.
Make the sauce. Add all of the ingredients for the sauce to a blender and blend on high until completely combined. Taste and adjust to your preference. Transfer the sauce to a bowl and chill in the refrigerator until ready to use.
Make the potato balls. Line a large baking sheet with parchment paper and lightly dust with flour. Stir 1 egg into the potato mixture. With lightly floured hands, take a spoonful of the potato mixture and flatten it into a disk. Add a cube of cheese to the center and wrap the potato mixture around it. Transfer to the prepared baking sheet. Repeat until you have no more potato mixture left. Place the baking sheet in the refrigerator while you prepare the next step.
Prepare a breading station with 3 bowls or small baking dishes. Add the flour to one, the beaten remaining eggs to one and the breadcrumbs to one. Make sure the eggs are beaten well and the two types of breadcrumbs are combined well. Coat each potato ball in flour, then egg and the breadcrumbs. Transfer to the baking sheet and place back in the refrigerator while preparing to fry.
Pre heat the oven to 350 degrees. Add the oil to a heavy bottomed pan fitted with a thermometer and heat to 300 degrees. Fry the potato balls in batches, making sure not to over crowd the pan, until golden brown on all sides. With a spider strainer or slotted spoon, transfer the potato balls to a paper towel lined plate and sprinkle lightly with salt. Transfer to a baking sheet and bake for 5 minutes until warmed through and cheese is melted.
Serve the cheesy fried Colcannon balls with the dipping sauce. Enjoy!