Warm a large dry skillet over medium heat. Add the panko and cook, stirring often, until deeply golden and crisp, 4–6 minutes. Transfer to a shallow bowl to cool, then stir in the salt, black pepper, and smoked paprika.
Heat the oven to 425°F (220°C). Lightly grease a mini muffin tin (you may need to bake in two batches or use two tins).
Portion the cold mac and cheese with a 1-tablespoon scoop (#60) and roll into compact balls with your hands. You should have about 30 bites. Arrange them on a plate or small tray.
Cover and refrigerate the balls for 20–30 minutes to firm up for cleaner breading.
Set up a 3-bowl breading station: flour in one shallow dish, beaten eggs in a second, and the seasoned panko in a third.
Bread each chilled ball: coat in flour and tap off excess, dip in egg, then roll in the seasoned panko, pressing gently so the crumbs adhere. For an extra-crisp shell, dip back into egg and crumbs a second time. Nestle each coated bite into a cup of the mini muffin tin.
Bake until the tops are richly browned and the centers are hot, 15–18 minutes, rotating the pan halfway. Let the bites stand 3 minutes, then loosen with a small spatula and serve warm.