Prepare the mixture for the croquetas the day before you plan to serve them, as it is best to let the mixture set in the refrigerator overnight.

Step 1:
Lightly oil a shallow 8-inch dish. Finely chop your dry-cured ham and add a pinch of salt.

Step 2:
Heat 2 tablespoons of olive oil and 4 tablespoons of butter in a saucepan on medium heat.

Step 3:
Once the butter has melted, add the flour and mix well, stirring until it is all blended.

Step 4:
Add half a cup of the milk, and increase the heat. Stir constantly. When the mixture starts to boil, add the rest of the milk and stir constantly until the mixture starts to thicken. Once it starts to thicken, lower the heat, and cook for a further 10 minutes, or until thickened.

Step 5:
Add the dry-cured ham to the mixture and stir in thoroughly. Cook for a minute or two, then pour into your prepared dish. Cover and refrigerate at least 2 hours - or preferably overnight - to allow the mixture to set.