Chop 4 of the white chocolate baking squares and melt the other 4 as directed on packaging. I prefer to use the microwave method. Starting with 30 second increments, stir until completely melted.
In a large bowl of the stand mixer, cream together butter and white sugar until fluffy. Add eggs one at a time. Mix until just combine and add in extracts and melted chocolate.
In another bowl combine flour, baking powder, salt. Add into the butter mixture alternating with the sour cream.
Preheat oven to 350 degrees. Prepare 10 inch bundt or tube pan by greasing or using cooking spray. Sprinkle the turbinado sugar around the pan as if dusting with flour.
Pour 1/3 of batter into bundt pan, sprinkle in 1/2 of chopped white chocolate & 1/2 of nuts. Repeat and then top off with remaining batter.
Bake for 55 to 60 minutes or until a toothpick, wooden pick or cake tester comes out clean. Cool 10 minutes in pan. Run a knife around the edges to loosen and turn over on a baking rack to cool.