Heat the olive oil in a large, deep sauté pan. Add the onion and garlic and fry until fragrant and translucent.
Add the rice, stirring to coat the rice in the oil then add the wine (if using). Allow to simmer for a minute or two then add the tomatoes, stock and peas. Season with salt and pepper.
Reduce the heat, cover and allow to simmer for 15 minutes or until the rice is just cooked and the liquid has been absorbed.
In the meantime, fry the shrimp in a very hot pan until golden brown on both sides (at this stage it's not necessary to ensure the shrimp are cooked through as they'll steam for another 5 minutes with the rice later).
Remove from the pan then add the butter and garlic and allow to cook for 30 seconds before deglazing the pan with the wine. Pour in the stock and lemon juice then allow to cook for 5 minutes until slightly reduced.
When the rice has absorbed the liquid, remove from the heat then add the shrimp. Cover with a lid and allow to steam for 5 minutes.
Serve the shrimp and rice with the garlic butter sauce, lemon slices and parsley.