Add the pecans, maple syrup, and vanilla to the pan.
Stirring constantly, cook for 3-5 minutes or until the syrup has caramelized. There should be no liquid left in the pan.
Scatter the pecans evenly onto a sheet of parchment paper. Working quickly and using a couple forks, spread the pecans so they don't clump together as they harden.
These harden within about 30 minutes, but it's best to let them cool for a couple hours before storing them in an airtight container. When not kept in an airtight container, they can get a little sweaty. They can be kept at room temperature for several weeks.