Melt 2 tablespoons of butter in a medium skillet over medium heat. Add 1 finely diced onion and sauté for 3–4 minutes until translucent. Stir in 2 chopped spring onions and cook for an additional 1–2 minutes.

In a large mixing bowl, combine the sautéed onions with 1 cup of crab meat, 1 teaspoon of salt, and ½ teaspoon of black pepper. Gently fold together.

In the same skillet, melt 2 tablespoons of butter over medium heat. Sprinkle in 2 tablespoons of all-purpose flour, whisking for 1–2 minutes. Gradually add 1 cup of whole milk, whisking until thickens.

Pour the thickened béchamel sauce into the bowl with the crab mixture. Stir gently to combine, and let it cool for about 15 minutes.

Dust your hands with flour. Shape about 2 tablespoons of the crab mixture into balls or patties.

Prepare a shallow dish with 1 beaten egg and another with 1 cup of panko breadcrumbs. Dip each croquette in the egg and roll in the breadcrumbs.

Heat ½ inch of neutral oil in a deep skillet over medium-high heat. Fry croquettes for 3–4 minutes on each side until golden brown.

Transfer fried croquettes to a paper towel-lined plate. Garnish with parsley and serve hot.