• 50g butter
• ½ tbsp extra-virgin olive oil
• 1 small onion, finely diced
• 200g cooked ham (smoked or unsmoked), finely chopped
• 50g plain flour, plus a little extra for dusting
• 300ml whole milk
• 150g blue cheese, crumbled or grated
• 1 heaped tsp Dijon mustard
• 1 egg, beaten
• 100g white breadcrumbs
• Light vegetable oil, such as sunflower oil, for frying
• Sea salt and freshly ground black pepper

Set a medium saucepan over a medium heat. Add the butter and olive oil and, once the butter is bubbling, stir in the diced onion. Cook gently for about 5 minutes until soft but not coloured. Add the chopped ham, season with sea salt and black pepper and cook for a further 2 minutes.

Sprinkle in the flour, stir well and cook for 1–2 minutes. Gradually add the milk, stirring continuously until you have a very thick, smooth sauce. Add the blue cheese and mustard and stir until well combined. Spread the mixture onto a tray or plate and leave to cool, then refrigerate until completely firm.

Once chilled, shape the mixture into balls or small quenelles. Dust lightly with flour, dip into the beaten egg, then coat well in the breadcrumbs.

Pour enough oil into a deep saucepan to come about 5cm up the sides and heat to 180°C, or until a small cube of bread turns golden in about 1 minute. Fry the croquettes in batches for 3–4 minutes until golden brown and crisp. Lift out with a slotted spoon, drain on kitchen paper and serve warm.