Roughly chop the pecans into small pieces.
In one mixing bowl, combine the dry ingredients. Sift the flour, salt, baking powder, and baking soda together so they are thoroughly combined.
Brown the butter by breaking the butter into chunks and melting it in a saucepan over medium heat. Wait for the butter to stop popping and bubbling, and then watch carefully until brown spots start to appear and it slightly darkens in color.
Take the browned butter off the heat and mix it thoroughly with the sugars. Allow it to cool for 5 minutes.
Slowly add the egg and egg yolk whilst stirring to incorporate it into the browned butter and sugar.
Now add the dry ingredients to the wet mixture whilst stirring to combine. Add the chocolate chips and chopped pecans and stir until you have a smooth and slightly sticky cookie dough.
Turn the cookie dough out onto a piece of plastic food wrap/cling film and shape it into a long log. Wrap it up and chill it in the fridge overnight for best results, or for a minimum of 4 hours.
Preheat the oven to 180 degrees Celsius/355 degrees Fahrenheit.
Unwrap the cookie dough and slice it into 1-inch pieces. Place the brown butter pecan cookies on a lined baking tray with a gap in between each one and press down sligtly to help them to spread.
Bake the cookies for 10 minutes or until they are golden and crispy at the edges but still slightly gooey in the middle. Leave them to cool for 20 minutes before transferring them to a cooling rack.