Grease a 9×13-inch baking dish or line it with parchment paper. Set aside.

In a large heavy-bottomed saucepan, combine sugar, milk, corn syrup, and butter. Stir over medium heat until the sugar is completely dissolved and the mixture begins to bubble.

Attach a candy thermometer to the side of the pan, and continue to cook while stirring frequently until the mixture reaches 236°F (soft-ball stage), usually taking about 15–20 minutes.

Remove the saucepan from the heat and stir in the vanilla extract.

Fold in the chopped pecans, ensuring they are well coated in the caramel.

Pour the hot mixture into the prepared pan, spreading it evenly with a spatula.

Let the candy cool completely at room temperature for about an hour.

Once set, cut into squares or rectangles and serve on a lovely platter.