In a heavy skillet on medium heat, combine pecans, sugar, and 2 TBSP butter, stirring constantly about 6 minutes, or until sugar has melted and browned. Remove heat, spread nuts on foil. Once nuts have cooked break into bite sized pieces. Set aside.
In a medium saucepan whisk together milk, brown sugar, egg yolks, and pinch of salt. Place pan on medium-high heat until mixture comes to a simmer. Lower the heat to medium and whisk mixture for 5 minutes or until it begins to thicken. Strain mixture into a large bowl and whisk in remaining 2 tablespoons butter until combined, then incorporate half and half, cream, and vanilla. Cover with plastic wrap and refrigerate 2 hours, or until chilled.
Pour mixture into ice cream maker, process according to manufacturer's instructions. Once ice cream is made stir in reserved pecans.