Preheat oven to 350°F. Line baking sheets with parchment paper.
In a large bowl, cream together butter, granulated sugar, and brown sugar until light and fluffy, about 2 minutes. Add eggs, one at a time, then add the vanilla extract.
In a separate bowl, whisk together flour, baking soda, and salt. Gradually add to the butter mixture and mix until just combined.
Stir in poppy seeds and walnuts until evenly distributed.
Drop dough by tablespoonfuls onto prepared baking sheets, 2 inches apart. Bake for 10 to 12 minutes, or until golden brown.
Remove from oven and let cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely.
Interesting Facts
Poppy seeds are known for their nutty flavor and crunchy texture.
Poppy seed cookies were popular in the 19th century in Europe.
Walnuts are a good source of healthy fats and protein.