Preheat over to 350°F. Grease a 12-cup Bundt pan with butter or cooking spray.
Open tubes of biscuit dough and separate into 16 pieces. In a gallon size plastic food bag, thoroughly mix the white sugar and cinnamon.
Working in batches of 4, drop the biscuits into the bag and toss to coat. Place the biscuits standing on the side with overlapping edges into the bundt pan. Repeat with remaining biscuits. Sprinkle any remaining cinnamon sugar over the biscuits in the pan. Place the walnuts between and on top of the biscuits in the pan.
Melt the butter in a medium bowl. When the butter is completely melted, add the brown sugar and stir until the brown sugar and butter are incorporated. Pour over the biscuits to coat.
Bake on the middle oven shelf for 40 minutes, until golden brown and crisp on the edges.
Allow to cool 5 minutes before inverting on a serving platter. Keep inverted for 1 minute before lifting off the pan. Allow carmel to drip from the pan. Serve warm!