Preheat oven to 350°. Bake walnuts in a single layer in a shallow pan 6 to 8 minutes or until toasted and fragrant. Pour 2 Tbsp. melted butter into a lightly greased 10-inch (14-cup) tube pan. Sprinkle 2 Tbsp. walnuts over butter in pan.
Melt 1/2 cup butter in a medium saucepan over medium heat. Add brown sugar, and cook 2 minutes or until sugar is melted and begins to bubble. Stir in cinnamon and remaining walnuts.
Cut each biscuit into fourths using kitchen shears or a knife. Place 40 biscuit quarters on top of walnuts and butter in pan. Top with half of brown sugar mixture. Add remaining 40 biscuit quarters, and top with remaining brown sugar mixture.
Bake at 350° for 20 to 25 minutes or until golden brown. Invert onto a serving plate, and serve immediately.
Note: For testing purposes only, we used Pillsbury Golden Layers Buttermilk Biscuits.