In a large bowl, mix mashed potatoes with chopped fresh dill. If starting from scratch, boil cubed potatoes until tender, mash with butter, milk, salt, coll completely and add fresh herbs.
Scoop potato mixture with an ice cream an ice cream scoop or a spoon. Flatten in your hand into a disk and place a cube of cheddar in the middle. Fold the edges to seal, and shape into a smooth even ball. Repeat with the rest of the potatoes and cheese.
Set up three shallow bowls - flour, beaten eggs, and a mix of breadcrumbs, black pepper, and onion powder.
First, roll a potato ball in flour and shake off any access. Dip in an bowl with whisked egg, coating the ball completely. Lastly, roll it in breadcrumbs, pressing gently to ensure it is evenly coated. Place breaded croquette on a parchment-lined board. Repeat with the rest of the balls.
For better results, chill breaded croquettes for 20-30 minutes in the fridge.
Preheat air fryer for about 5 minutes. Spray the basket with some cooking spray. Place croquettes in a single layer and lightly spray them with oil on top. Air fry at 390°F for 4-7 minutes until golden brown. No flipping requires, unless you see that they are cooking unevenly.
Enjoy hot with ketchup or your favorite dipping sauce.