Preheat oven to 350° F. Spray a 9x13 inch baking pan with non-stick spray.
In an eletric stand-mixer cream butter and sugar together until creamy and fluffy. Beat in eggs, one at a time, and vanilla extract until just combined.
In a separate medium bowl, combine flour, baking powder and baking soda. Whisk together. Slowy add flour mixture to the wet mixture, just until combined. Stir in white chocolate chips.
Spread batter evenly (it will be thick!) into the bottom of the prepared pan. Bake for 25 to 28 minutes or until toothpick inserted in center comes out mostly clean. (Don't overbake!)
Let blondies cool at least 10 minutes before cutting into squares.