How to Make It
In a large bowl, combine the mashed potatoes with the chicken, shallots, egg, chives, salt, pepper and the 2 tablespoons of bread crumbs; mix well. Cover and refrigerate for 2 hours.
Line a baking sheet with wax paper. Form the chicken mixture into six 1/2-inch-thick patties. Dredge the patties in bread crumbs and transfer them to the baking sheet. Cover and refrigerate until firm, about 1 hour.
In a large skillet, heat 1/4 inch of oil until shimmering. Fry the croquettes over moderately high heat, turning once, until golden and hot throughout, 4 to 6 minutes total. Transfer to paper towels to drain; serve hot.