Preheat your oven to 200°C/400°F/gas mark 6 and line a baking sheet with parchment paper.
Place each chicken breast between two sheets of parchment paper or cling film and gently pound them to a thickness of about 1/2cm.
Sprinkle both sides of the chicken with sea salt and freshly ground black pepper.
Mix together the plain flour, salt, and pepper on a shallow plate.
Beat the extra large egg with water on a separate plate. Spread the seasoned dry bread crumbs on a third plate.
Dip each chicken breast first in the flour mixture, shaking off any excess, then dip it into the beaten egg mixture, and finally coat it with the breadcrumbs, pressing gently to ensure they adhere well.
Heat 1 tablespoon of olive oil in a large sauté pan over medium to medium-low heat
Add the coated chicken breasts and cook for approximately 2 minutes on each side until they turn golden brown.
Transfer the browned chicken breasts to the prepared baking sheet and let them continue cooking in the oven for 5 to 10 minutes while you prepare the sauce.
Wipe out the sauté pan with a dry kitchen towel, then melt 1 tablespoon of unsalted butter over medium heat.
Add the freshly squeezed lemon juice, dry white wine, the reserved lemon halves, salt, and pepper to the pan.
Allow the mixture to boil over high heat until it reduces by half, usually taking about 2 minutes.
Remove the pan from the heat and add the remaining 2 tablespoons of the unsalted butter, swirling it in to combine.
Discard the lemon halves and serve one chicken breast on each plate.
Spoon the luscious lemon sauce over the chicken and garnish with a slice of lemon and a sprinkling of fresh parsley.