Preheat oven to 350℉. Line a large baking sheet with parchment paper. Set aside.
In a large mixing bowl, using an electric hand mixer, mix together butter and sugar until creamy. Add eggs, one at a time, along with the vanilla, and mix until fluffy and creamy. Set aside.
In another bowl, mix together flour, baking powder, baking soda, and salt.
Add the flour mixture to the butter mixture gradually, alternating with the buttermilk, starting and ending with the flour mixture.
Stir in the dates and walnuts.
Using a tablespoon sized scoop, drop cookie dough portions onto prepared baking sheet. Bake for 13-15 minutes, or until edges are slightly brown and top of cookie no longer looks wet.
Remove from cookie sheet and cool on wire cooling rack.
Notes
Cookies will likely need to be baked in batches. Bake time is per batch of cookies.