Step 1: Prepare the Dough

1. In a large bowl, cream together softened butter and granulated sugar until light and fluffy.
2. Add eggs, one at a time, mixing well after each addition. Stir in vanilla extract.
3. In a separate bowl, whisk together flour, baking powder, and salt.
4. Gradually add the dry ingredients to the wet ingredients, mixing until combined.
5. Divide the dough into two portions, wrap each in plastic wrap, and refrigerate for at least 30 minutes.

Step 2: Prepare the Filling

1. In a medium bowl, combine ground walnuts, granulated sugar, powdered sugar, cinnamon, and nutmeg.
2. Stir until the mixture is evenly blended.

Step 3: Assemble and Bake

1. Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper.
2. Roll out one portion of the chilled dough on a floured surface to a thickness of ¼ inch.
3. Spread half of the nut filling evenly over the dough. Roll the dough tightly into a log.
4. Slice the log into 1-inch pieces. Repeat with the remaining dough and filling.
5. Arrange the slices on the prepared baking sheet, spacing them slightly apart.
6. Bake for 12-15 minutes or until golden brown.
7. Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.