Melt the butter in a pan and fry the onions until they're translucent. Add the rice, let it sweat, and then season with salt and pepper. Now pour in the water and leave everything to simmer until the rice is cooked. Stir in the parsley and parmesan until the cheese has melted. Leave everything to cool.
Take some of the rice mix and flatten it in your hand. Place a cube of cheese in the middle and form a ball around it with the rice.
Roll the ball in flour, egg, and then breadcrumbs in that order. Now press it slightly flatter and place it on a baking tray.
Pour a little oil on all of the croquettes and bake them at 360°F for 15 minutes. You can also fry the croquettes.