Melt the butter in a pan over medium heat until it is fully liquid, ensuring it does not brown.

Add the flour gradually while stirring continuously to form a roux. Cook the roux for about 1-2 minutes to eliminate the raw flour taste.

Slowly pour in the semi-skimmed milk, whisking constantly until you achieve a smooth, thick sauce. This should take a few minutes, so be patient and keep stirring.

Season the sauce with freshly ground pepper, salt, and a pinch of ground nutmeg, giving it a flavorful twist.

Incorporate the brown shrimp into the sauce and allow the mixture to cool slightly.

Mix in the egg yolk thoroughly with the shrimp and sauce blend to create a creamy consistency.

Using your hands, form small croquettes from the mixture, making sure they are compact and uniform in size.

In a separate bowl, beat the egg until smooth.

Dip each croquette first into the egg, allowing any excess to drip off, then coat them thoroughly with breadcrumbs to give them a crunchy exterior.

In a clean pan, heat more butter over medium-high heat until it sizzles.

Fry the croquettes in the hot butter, turning them occasionally, until they are golden brown and crispy, which should take about 3-4 minutes.

Drain the croquettes briefly on paper towels to remove any excess oil before serving. Enjoy your delicious shrimp croquettes!