In a small skillet over medium heat, cook pecans in butter until lightly browned and fragrant, stirring constantly, about 3 to 5 minutes. Set aside.
Whisk eggs in a mixing bowl; set aside. Combine brown sugar and half and half in a saucepan and mix well. Bring to a boil over medium-high heat; remove from heat. Gradually pour hot mixture into the eggs, whisking constantly. Return custard to saucepan and cook, stirring occasionally, until mixture coats the back of a spoon (see Editor's Note). Remove from heat and stir in cream, vanilla, and pecans.
Pour into ice cream maker and freeze according to manufacturers' directions.
