Bring a pot of salted water to a boil. Add the macaroni and cook until al dente. Drain well and set aside.
In a medium saucepan, melt the butter over medium heat. Sprinkle in the flour and whisk for 1 minute. Slowly pour in the warm milk, whisking constantly, and cook until it begins to thicken. Stir in the cheddar cheese until melted and smooth, then season with salt and pepper.
Fold the cooked macaroni into the cheese sauce. Spread the mixture into a shallow dish, cover, and refrigerate for at least 2 hours or until firm enough to roll.
Scoop the chilled mixture and roll into balls about 1½ inches (4 cm) wide. Place on a tray.
Coat each ball lightly in flour, dip into the beaten eggs, then roll in panko until fully coated. Set back on the tray.
Heat oil in a deep pot to 350℉. Fry the mac and cheese bites in batches for 2-3 minutes or until crisp and golden. Transfer to a paper towel–lined plate.
To make the dipping sauce, whisk together Greek yogurt, French mustard, olive oil, cilantro, salt, and pepper until smooth. Refrigerate until serving.
Sprinkle with parsley and serve hot with the yogurt mustard sauce.