Your first step to make a Spanish ham and cheese croquettes recipe is to cuprepare the ham. The smaller they are the easier it is to form balls with them.
Use one small pot to add the milk and ham in it and put it to cook on medium heat. Then, put the buttor in another small pot and melt it on the stove/in the microwave, but do not bring it to boil!
Cook the milk with the ham just for about 6 minutes and turn off the heat. Leave it a few minutes to cool, then add the melted butter.
Use a blender to blend it together well, so you can later form balls. Don't over-blend it though, make sure small pieces of ham remain visible. Shredd the Gouda cheese, and the Parmesan.
Add the cheese to the other ingredients and mix them together well, also season with salt and pepper after taste. Then, put the croquette mix in the fridge so it can thicken.
Once it got thick enough, you have to form little balls, or you can make also longer shape.
Beat up an egg with a teaspoon of flour and a few drops of milk and heat up the oil in a skillet. Add enough oil to cover completely the croquettes.
Once the oil is hot, dip your croquettes into the egg mix, and place them right away in the skillet. Fry them on medium heat for about 4 minutes. They are ready when they get a golden color.