Squeeze the juice from one and a half lemons and reserve. Cut the remaining half lemon into very thin slices. Remove seeds and set the lemon slices aside.
Season the chicken scallopini with salt and pepper. Dredge in flour, coating both sides, and tap the excess flour off. Heat 3 tablespoons of olive oil and 2 tablespoons of butter in a large skillet over medium heat. Add as many scallopini into the pan that will fit without touching, and cook until golden brown, approximately 3 minutes. Flip and cook second side until lightly browned, about 2 minutes. Remove scallopini and drain on paper towel.
When done with the scallopini, wipe off the fat from the skillet with paper towels. Add the remaining 3 tablespoons of olive oil, butter, garlic, and lemon juice and slices to the skillet. Cook, scraping the bottom until garlic is golden brown, about 3 minutes. Scoop out the lemon slices and set aside. Add the caper berries and olives and cook, stirring gently for about 4 minutes. Pour in wine and bring to a boil. Cook until the wine is reduced by half. Add the chicken stock and boil until slightly syrupy. Return the scallopini to the skillet and coat each piece in the sauce. Add parsley and swirl into sauce.
Divide scallopini onto separate plates. Spoon the sauce over, and add the caper berries and olives around scallopini. Add some of the spinach on the side. Finish by decorating each plate with reserved lemon slices on top of the scallopini.
Heat olive oil in large skillet over medium heat. Crush garlic cloves with the side of the knife and add to the oil. Cook until golden brown, approximately 2 minutes. Add the spinach in handfuls, and season lightly with salt and pepper, and cover pan. Cook until spinach releases its liquid. Uncover pan, and cook stirring until spinach is wilted and water has evaporated. Taste and season with additional salt and pepper.
Recipe courtesy of William Gallagher, Becco's, New York, NY