This is a rich way of cooking big prawns called gambones in Spanish, although it is not authentically malagan (for Málaga there is too much butter and too little olive oil). They usually come frozen or thawed but very rarely fresh but they still taste good. I had them many times in Valencia but I am not sure what is the origin of this recipe because when I asked in Valencia no one wanted to confirm the origin.
Remove the shells from the tails of the prawns but keep the head, remove the dark digestive cord. This is important as the heads release their juices and emulsify the butter-lemon mixture. Extract juice from one lemon and keep in a glass. Chop the garlic and parsley.
Preheat oven to 220°C. Spread 50g of butter at the bottom of the baking dish. Place the prawns at the bottom and cover them with small cubes of the rest of the butter, pour over the lemon juice, salt lightly and sprinkle with breadcrumbs. Transfer the dish into the oven for 5-7 minutes or until the breadcrumbs get golden brown colour. Remove from the oven. Season with chopped parsley. Serve with white bread.