Preheat the oven to 350°.
Butter and flour a 12 cup Bundt pan or two six cup (standard size) bread pans.
Finely grind the chopped walnuts in a food processor. Chopping them into pieces keeps them even in texture at the end of grinding.
Sift flour, baking powder and salt into a medium-sized bowl.
With an electric mixer, beat the butter and sugar together in a large bowl until light and fluffy. Add one egg at a time, beating well after each one.
Beat in maple syrup and vanilla, and if you use it, maple flavoring.
Mix the dry ingredients into the wet ingredients.
Using a spatula, fold in the ground walnuts. Don’t stir.
Pour batter into prepared pan(s). Bake the pound cake until the top is golden brown and the cake tester comes out clean, about an hour.
Transfer pan(s) to a cooling rack. Let sit for 10 minutes. Run a butter knife around the edge of the cake to loosen it before removing the cake from the pan.