In a large bowl, cream together the butter, brown sugar, and white sugar until light and fluffy.

Add in the egg and vanilla and mix until combined. 

Fold in the flour and chopped pecans.

Bring the dough into a ball and divide in half. Roll each half into an 8 inch log, then wrap it in plastic wrap. Twist the ends of the plastic wrap tightly to create a compact even log. Chill the dough for 2 hours to over night. 

When ready to bake, pre-heat your oven to 350°F (180°C) then line 2 cookie sheets with parchment paper. 

Remove the logs of dough from the fridge and unwrap them. Using a large sharp knife slice each log into 1/2 inch rounds.

Arrange the sliced cookies on the cookie sheets about 1 inch apart. 

Bake the cookies for 18-20 minutes or until lightly golden and slightly crispy.

Transfer the cookies to a wire rack and allow the cookies to cool completely.

Cover and store the cookies in an airtight container for up to 3 days.