Line a 9x5-inch loaf pan with parchment paper or butter well.
Combine the chocolate chips, sweetened condensed milk, and butter in a medium saucepan. Place over medium heat.
Cook, stirring constantly, until the chocolate is melted and the mixture is smooth.
Remove from the heat and stir in the vanilla extract.
Stir in all but a couple tablespoons of the pecans. Pour into the prepared pan. Use a spatula to smooth out the top, then top with the remaining pecans.
Refrigerate the fudge until set, then cut into 1-inch squares.
Notes
Nutrition information provided as an estimate only. Various brands and products can change the counts. Any nutritional information should be used as a general guide.