Heat half the olive oil over a medium heat and add the onions. Sweat without browning for 7 minutes, stirring regularly. Add the garlic, stir, and cook for a further 3 minutes. Set aside to cool a little.
In a large mixing bowl combine the pork, breadcrumbs, tomato puree, Parmesan cheese and ground fennel seeds. Grate the zest of the orange and add this to the bowl. Remove the thyme leaves from the sprigs and add these too, and season with salt and pepper. Mix well with your hands until everything is well combined. Add the cooled onion and garlic and mix some more. Make golf-ball sized balls from the pork mixture.
In a heavy oven-proof lidded pan, heat the remaining oil over a medium heat and carefully add the meatballs. They should all fit snuggly in a single layer. After a couple of minutes turn the meatballs over using a palette knife - tongs may break them apart - and continue cooking and turning until browned on all sides but not cooked through.
Add the white wine and let it bubble away for 20 seconds then carefully pour in the passata and water. Add the orzo, making sure all the grains are covered with liquid. Add the bay leaves, sugar and more salt and pepper. Bring to a very gentle boil, cover with a lid and transfer to the oven for 25-30 minutes. Check halfway through cooking and add a little more water if the sauce looks like it's drying out. It's ready when the orzo is completely tender, the tomato sauce is bubbling and the kitchen smells amazing.