Add the flour and KEEN’S mustard powder and cook, stirring for 1-2 minutes. Reduce the heat and slowly add the milk a little at a time, whisking to ensure no lumps. Cook for 10 minutes until thickened. Add the cheese and stir until melted.
Remove from the heat and stir through the egg and ham. Season to taste with salt and pepper.
Spread mixture onto a baking sheet and let cool completely.
Scoop tablespoons of cooled mixture and shape with floured hands into ovals.
Dust each oval in flour, egg wash then coat evenly with the breadcrumbs. Transfer to a baking sheet lined with kitchen paper.
Heat vegetable oil in a large heavy based saucepan to 180℃.
Cook in batches for 3-4 minutes until dark golden brown, turning in the oil occasionally.