Preheat oven to 300 degrees F (150 degrees C) Grease cookie sheets.
In a large bowl, cream together the butter and brown sugar until smooth. Beat in the eggs and vanilla, then stir in the pumpkin puree until well blended. Combine the flour, baking soda, and pumpkin pie spice; stir into the pumpkin mixture. Fold in the white chocolate and pecans. Drop by heaping spoonfuls onto the prepared cookie sheets. Cookies should be at least 2 inches apart.
Bake for 20 to 22 minutes in the preheated oven, until bottoms are lightly browned. Cool for 5 minutes on baking sheets before removing to cool on wire racks.