In a large mixing bowl, beat the softened unsalted butter and packed dark brown sugar together with an electric mixer on medium speed for about three minutes, or until the mixture is light and fluffy.

Add the pure vanilla extract and the large egg to the butter-sugar mixture and mix until well incorporated. Then add the grade B maple syrup and continue mixing until everything is smoothly combined.

In a separate bowl, vigorously whisk together the all-purpose flour, baking soda, and salt to ensure they are well mixed and aerated.

Slowly add the flour mixture from Step 3 to the butter mixture from Step 2, mixing only until just incorporated to avoid overworking the dough. Gently fold in the roughly chopped walnuts until evenly distributed. I like to under-mix just a little to keep the cookies tender.

Cover the cookie dough with plastic wrap and chill it in the refrigerator for thirty minutes. This helps prevent the cookies from spreading too much during baking.

Line cookie sheets with parchment paper. Scoop out spoonfuls of the chilled dough, forming them into balls about 1 inch in diameter, and arrange them on the prepared baking sheets with space in between.

Bake the cookies in a preheated 350°F oven for 10 to 12 minutes, or until lightly browned around the edges. Allow the cookies to cool on the sheet for a minute or two before transferring them to a wire rack to cool completely. For a chewier cookie, I take them out when the centers still look just slightly underdone.