Preheat the oven to 375 degrees F (190 degrees C). Line a 12-cup muffin pan with paper baking cups.

Sift together flour, baking powder, and salt in a large bowl; set aside.

Cream butter and sugar in a mixing bowl until light and fluffy. Stir in maple syrup and eggs; beat until well blended. Add flour mixture alternately with milk, beating just until combined. Stir in walnuts. Spoon batter into the prepared muffin cups, filling each about 3/4 full.

Bake in the preheated oven until a toothpick inserted into the center of a muffin comes out clean, about 20 minutes. Remove to a wire rack to cool completely.