How to Make It
Preheat the oven to 300°. In a skillet, toast the pine nuts over moderately high heat, stirring, until golden brown, 2 minutes. Transfer to a small plate.
In the same skillet, heat the oil. Season the chicken breasts with salt and pepper and add them to the skillet skin side down. Cook, turning once and pressing with a spatula, until browned on both sides, about 6 minutes. Transfer the chicken breasts to a large rimmed baking sheet and bake in the oven until just white throughout, about 20 minutes.
Meanwhile, add the leeks and shallots to the skillet and cook over moderately low heat, stirring, until softened, 7 minutes. Add the wine, increase the heat to high and boil until reduced by half, about 3 minutes. Add the stock and boil until reduced to 1/2 cup, about 10 minutes. Off the heat, swirl in the butter 1 tablespoon at a time. Season the sauce with salt and pepper. Transfer the chicken to plates. Pour the sauce over, garnish with the pine nuts and serve.