Line a baking sheet or plate with parchment paper.
Scoop the chilled macaroni and cheese into 1½-inch balls (about 2 tablespoons each) and place them on the prepared baking sheet.
Freeze the macaroni and cheese balls for 20-30 minutes, or until firm. This helps them hold their shape while breading and frying.
In a shallow bowl, whisk together the eggs and milk until combined.
Place the panko bread crumbs in a second shallow bowl.
Dip each macaroni and cheese ball into the egg mixture, allowing any excess to drip off. Then roll it in the panko bread crumbs until completely coated. Place the breaded balls back on the baking sheet.
Pour 2-3 inches of vegetable oil into a large heavy-bottomed saucepan or deep skillet. Heat the oil to 350°F.
Working in batches, carefully lower the macaroni and cheese balls into the hot oil. Fry for 2-3 minutes, turning occasionally, until all sides are golden brown and crispy.
Remove with a slotted spoon and transfer to a paper towel-lined plate to drain any excess oil.
Serve immediately with your favorite dipping sauces such as ranch, marinara, or spicy aioli.