Combine first 3 ingredients in a bowl and set aside. Preheat oven to 375F (190C). Toast walnuts.

Cream butter; add sugar and beat with electric mixer until mixture is fluffy. Add egg and vanilla; beat to combine.

Add flour mixture into butter mixture and mix. Stir in raisins, cranberries and walnuts.

Let cookies cool about 5 minutes on the sheets, then transfer them to a wire rack.