Grease a 10-inch Bundt pan. Sprinkle the bottom of the pan with ½ cup of walnuts, set aside.
Mix the white sugar and cinnamon in a large zip top bag. Cut each biscuit into quarters. Place 10 biscuit pieces into the bag with the sugar/cinnamon mixture. Shake until each of the pieces are completely coated. Add the sugar coated biscuits to the prepared pan. Topping with ½ of the remaining walnuts. Continue until all the biscuits and remaining walnuts are in the pan.
In a medium skillet, melt the butter over medium-low heat. Once the butter has melted, stir in the brown sugar and vanilla extract. Stir until combined, but not long enough for it to separate, about 1 minute.
Carefully pour the brown sugar mixture into the Bundt pan over the biscuit pieces. Shake it back and forth a few times to ensure that the walnut pieces are well coated and don’t stick to what will be the top. Bake for 30-35 minutes, until golden brown and no longer doughy in center. Loosen edges of the pan with a spatula. Cool in the pan for 5 minutes. Turn upside down onto serving plate.