1. Preheat oven to 350.

2. In a food processor fitted with the metal blade, place the 1 cup of walnuts and process coarsely. Add 1/4 cup of the brown sugar and process finely; set aside.

3. Combine the butter, the remaining 1/2 cup brown sugar, maple extract, and salt in a large bowl. Use an electric mixer set on high and beat until light and fluffy. Reduce the speed to low; add the flour and the nut mixture and mix just until incorporated.

4. Roll pieces of dough between your hands to form 1-inch balls. Arrange on ungreased baking sheets about 1 1/2 inches apart. Press a walnut half into the center of each.

5. Bake the cookies until brown around the edges, about 20 minutes. Transfer to wire racks to cool. Store at room temperature for up to 5 days.