Here is the final recipe for this particular putxero.  Using the rest of your leftovers, plus a couple of extras, you can make a whole meal of these little golden dumplings.
This particular recipe is hotly debated in the family. Should you add bechamel? Should you use a blender instead of a mortar and pestle, to make the ingredients smooth?  If I were to follow Iaia to the letter, I would answer yes to both of those questions, but Auntie Toni has convinced me that la abuela (Oscar’s grandmother) didn’t do either and that her mandonguilles were the best ever…I’ll let you experiment and decide for yourself!

What you need: leftovers from the putxero
1 onion
1 clove of garlic
a small bunch of parsley
about 30g of pine nuts
1 or 2 eggs
1/2 tsp sweet paprika
sunflower seed oil for frying

What you do: Finely dice your onion and fry gently in a little olive oil until it softens. While it is cooking, grab a mortar and pestle and smoosh your garlic and parsley, adding a pinch of salt to help grind everything up.  Once the onion is softened, stir in the garlic/parsley mix and the tsp of paprika. Fry for 20 to 30 seconds, then remove from the heat.
Take your leftovers and mortar and pestle them in manageable batches. (I don’t include the fat at this stage because I prefer to finely chop it rather than squash it). You want things to be chunky but not whole; it isn’t very taxing, nor is it a precise art, so smoosh to please yourself.  In a large bowl, mix the onion, garlic and parsley into the mashed putxero leftovers. Add the finely chopped fat and the pine nuts. Mix well.
Put a frying pan with a couple of centimetres of sunflower oil on to heat. The hotter the oil, the less oily your finished croquettes will be.  The egg (which is essential for binding the croquettes) can be dealt with in two ways, I tried both today, and it makes no difference whatsoever.
1. Beat an egg and then stir into the mixture before forming little croquette-shaped balls and frying, or
2. Make the little balls first and then dip them into a beaten egg before popping them into the pan.
Let the croquettes turn golden on one side before attempting to move them, and then do so gingerly so that they don’t fall apart. Drain on kitchen paper and allow to cool slightly before gobbling them up, or you will burn your mouth! Easy peasy.