Start by placing the potatoes in a small saucepan and cover them with water. Cook on medium-high heat until the potatoes are tender, about 15 to 18 minutes. Keep an eye on them to ensure they don't overcook. Once tender, drain them and set aside.
In a large bowl, mash the cooked potatoes. You want a smooth consistency, but a few lumps can add texture. Then, combine the mashed potatoes with the tuna, dill, mayonnaise, red onion, Dijon, lemon juice, salt, and black pepper. Mix everything well to ensure all the flavors meld together beautifully.
Once mixed, place the bowl in the freezer for about 10 minutes. This helps the mixture firm up, making it easier to shape.
After chilling, take a generous 1/4 cup of the mixture in your hands and gently roll it into a log shape. You should be able to form about 8 logs. Make sure they are compact but not too tight.
Set up a small breading station: place the beaten egg in one bowl and the panko in another. First, dip each croquette in the egg, allowing any excess to drip off. Then, roll it in the panko, ensuring it's well coated.
Once breaded, place the croquettes on a board or plate and spray both sides with olive oil. This will help them achieve that golden-brown texture.
If using an air fryer, preheat it to 350°F (175°C). Place the croquettes in the basket and cook for about 10 minutes, turning them halfway through. They should be golden and crisp when done.
If you prefer to bake them, preheat the oven to 375°F (190°C). Arrange the croquettes on a baking sheet and bake for 22 to 24 minutes, flipping halfway for even cooking.
Once crisp and golden, remove from the air fryer or oven. Serve your Tuna Croquettes with fresh lemon wedges for an extra burst of flavor!