Preheat oven to 350° and line baking sheet with parchment paper.
In mixing bowl, beat butter until creamy. Scrape sides and add sugars - beat until fluffy.
Add eggs one at a time, beating after each addition, then add vanilla and mix.
Add flour, baking powder and salt to wet mixture and beat on low speed, until just incorporated, then increase speed to medium and mix another 30 seconds.
On low speed, mix in white chocolate and chopped nuts and mix only until blended, careful not to overmix.
Places rounded drops of cookie dough about 2 inches apart on lined baking sheet. Bake about 10-12 minutes, or until lightly golden.