Preheat your Yoder Smoker YS640 to 350ºF. Sift into a bowl the baking powder, baking soda and flour. Add the salt and chopped nuts and whisk briefly.
Combine the brown sugar and melted butter in the bowl of a stand mixer. Mix on medium/low with the paddle attachment until well combined. In a separate small bowl, whisk together the egg and vanilla extract. Add the egg mixture to the brown sugar mixture. Mix to combine.
Add the flour mixture, a little at a time, until mixed well mixed then add the white chocolate chips. Spread out dough in a Lodge Logic 12” Cast Iron Skillet. Bake on the second shelf until a toothpick inserted in the center comes out clean, about 30 minutes. The internal temperature will be about 200ºF. You can check the temperature with an instant read thermometer like the Maverick PT-75.
While the blondie is baking, make the Maple Butter Sauce. Heat the maple syrup and butter in a sauce pan. When the butter is melted add the brown sugar. Whisk over the heat until the sugar is dissolved. Hold warm. Serve the blondie warm with ice cream and the Maple Butter Sauce.