Preheat your oven to 350 and line a cookie or baking sheet with parchment paper.
In the bowl of an electric mixer fitted with a paddle attachment, cream butter and sugar together on medium low speed until slightly lighter in color, about 1-2 minutes.
Add beaten egg and 1 tablespoon of maple extract to the bowl. Mix on medium low until just combined, about 1 minute. The batter will look lumpy and almost curdled, don’t worry, it will become smooth with the additional ingredients.
With the mixer on low, add flour, baking soda, baking powder, and pinch of salt. Increase the speed to medium low and mix until the butter mixture is incorporated to the dry ingredients, about 1 minute. It will still be very dry and crumbly.
Finally, add the sour cream and walnuts to the bowl and mix on medium low speed until well combined and smooth, about 2 minutes.
Using an ice cream scoop, fill the scoop about 1/2 full with dough and drop onto a parchment lined baking sheet. Space the scones about 1-2 inches apart on the baking sheet.
Place scones on middle rack in oven and bake for 25-30 minutes, or until scones are lightly browned on top. Let cool slightly before toping with the glaze.