Melt butter in a small skillet over medium heat. Cook and stir pecans in hot butter until lightly browned and fragrant, 3 to 5 minutes. Set aside.

Whisk eggs in a large bowl; set aside.

Combine half-and-half and brown sugar in a saucepan and mix well. Bring to a boil over medium-high heat; remove from heat.

Gradually pour hot mixture into eggs, whisking constantly. Return custard to the saucepan and cook, stirring occasionally, until the mixture thickens enough to coat the back of a spoon. The custard mixture is ready when you can draw your finger down the back of the coated spoon and see a clear line. Remove from heat and stir in cream, pecans, and vanilla; allow mixture to cool slightly.