Preheat oven to 350°F and line 2 baking sheets with parchment paper.
In a medium bowl, combine flour, baking soda, and salt. Set aside.
In the bowl of a standing mixer with the paddle attachment or a using a handheld mixer, combine butter and brown sugar, mixing until smooth, around 1-2 minutes.
Beat in the egg until combined. Add in the maple syrup, vanilla, and maple extract and mix until combined, scraping down the sides of the bowl often.
Add in the dry ingredients and mix on low speed until combined. Add in the chocolate chips and walnuts and mix on low again.
Use a medium cookie scoop or your hands to roll the dough into round balls, about 1.5 tablespoon-sized. Add more nuts and chocolate chips on top if desired. Bake the cookies one tray at a time for about 8-11 minutes. Remove them from the oven when the edges are slightly brown and look set. The middles will look soft!
Let the cookies cool on the baking sheet for about 5-10 minutes then transfer them to a wire rack to cool completely.
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Notes
MEASURING THE FLOUR: It's important to properly measure the flour. Either measure your flour using a kitchen scale or use the proper scooping method: fluff the flour in the bag/container with a fork then use a spoon to scoop the flour into the measuring cup, then run the back of a knife along the top of the cup to even it out. Storage and Freezing Instructions:These cookies should be stored in an airtight container at room temperature and will stay fresh for up to 5 days.To freeze the cookies, place them in a freezer ziploc bag for up to 3 months. Thaw at room temperature.