In a large skillet, toast the pecans over medium high heart for a few minutes.

Line 2 large baking sheets with parchment paper and spray with nonstick cooking spray.

Arrange the toasted pecans in groups of 3 leaving about an inch of space between each group. Set aside.

In a medium saucepan, melt the butter over medium-high heat.

Stir in the brown sugar, corn syrup, and sweetened condensed milk. Cook and stir continuously until it reaches 235-240F on a candy thermometer.

Remove from heat and stir in the vanilla.