1. Melt butter in a small skillet over medium-low heat. Add pecans, and cook, stirring constantly, 6 to 8 minutes or until toasted and fragrant.
2. Whisk together mayonnaise and next 3 ingredients in a large bowl; stir in chicken and next 3 ingredients just until blended. Add salt and freshly ground pepper to taste. Cover and chill 2 to 24 hours; stir in 1/2 cup toasted pecans just before serving. Sprinkle with remaining pecans.