How to Make It
Pour 1/4 cup of the white wine into a small bowl. Crumble in the saffron and let stand for 5 minutes. On a large rimmed baking sheet, drizzle the saffron wine over the chicken; rub it in and let stand for 10 minutes.
Meanwhile, in a medium skillet, melt the butter. Add the leeks and cook over moderate heat, stirring occasionally, until softened, about 5 minutes. Stir in the nutmeg and the remaining 1/4 cup of white wine. Simmer for 1 minute. Add the chicken stock and sherry and bring to a boil. Transfer the mixture to a slow cooker.
Season the chicken with salt and pepper and add it to the slow cooker. Nestle in the garlic cloves. Cover and cook on high heat for 2 1/2 hours, shifting the chicken and garlic around a few times, until the chicken is cooked through and the garlic is soft. Add the olives, cover and cook for 15 minutes. Season with salt and pepper.
Serve the chicken stew in shallow bowls, with toasted bread for dunking (and for spreading garlic on).