1/3 cup sunflower oil + some more for deep frying 1/2 onion, finely chopped 3 cups warmed milk (hot to touch, 110°F) 2/3 cups flour salt, white pepper & ground nutmeg ¼ cup Serrano ham, diced ¼ cup roasted chicken, finely chopped 1 medium egg, boiled, shelled & finely chopped For rolling the croquetas 1/3 cup flour 2 eggs beaten 1 cup fine breadcrumbs
1 Heat oil in large frying pan over medium heat. Add onion and cook until soft and golden.
2 Add flour to the onion, cook for about 2 minutes stirring constantly until it starts to bubble. Stir in warmed milk slowly, stirring constantly to prevent from lumps to form (if you start to see any lumps, give the mixture a vigorous stir to get rid of them) when you finish adding all the milk, simmer for 2 minutes. Season with salt, white pepper and nutmeg.
3 Add Serrano ham, chicken and egg to the white sauce (Bechamel) stir to combine all ingredients. Transfer mixture to a greased tray. Level with a spoon & spray with a little more oil. Cover with cling film touching the mixture. Let cool slightly them place in the fridge until totally chilled and set.
4 Prepare 3 containers, place beaten egg and breadcrumbs in 2 separate bowls and flour in a small dish. Get heaped spoons of mixture, roll in flour first to help shaping and form a cylinder of about 2 1/2 in long - they don't need to be perfect. Dip croquetas in egg and roll in breadcrumbs to completely cover. Let them rest uncovered for 30 minutes.
5 Heat oil in deep frying pan (croquetas need to be submerged) to 350°F. Deep fry croquetas in small batches (don't overcrowd the pan) until golden, trying to keep temperature stable. They should be golden on the outside and heated through on the inside.
6 Gently transfer them to paper towels to drain off excess oil.