Preheat the oven to 350℉ degrees.

In a large mixing bowl, beat together sugars, oil, and eggs until smooth with a whisk.200 grams sugar, 165 grams brown sugar, 180 grams oil, 3 eggs

Then add the sour cream, vanilla, and sourdough discard, and stir until combined. 240 grams sour cream, 14 grams vanilla extract, 180 grams sourdough discard

In a separate medium bowl mix together the baking soda, salt, and flour. 7 grams baking soda, 5 grams salt, 350 grams flour

Fold the dry ingredients into the wet ingredients until just moistened. It’s ok if it is lumpy. Don’t overmix because this will cause a tougher texture.

In a separate bowl, mix together cinnamon, sugar and chopped nuts. 8 grams cinnamon, 150 grams sugar, 120 grams walnuts, chopped

Heavily spray a bundt cake pan with non-stick spray ensuring to get the inner and outer rims. You can brush oil on the pan instead but I wouldn't recommend greasing the pan with butter as the milk solids can act like glue.

Pour half of the cake batter into the pan and sprinkle the cinnamon sugar mix on top (it’s a thick layer). Using a toothpick swirl the cinnamon sugar and then pour the remaining batter on top.

Bake for 50-60 minutes. To ensure the coffee cake is done, place a toothpick in a few spots around the coffee cake. If the toothpick comes out clean, then it is ready to be removed from the oven.

Once baked, let the coffee cake sit for 5-10 minutes in the pan to set before placing on a cooling rack. I don’t recommend letting it completely cool in the pan as that can make the edges tough. Take a spatula and gently run it along the sides of the pan to ensure the coffee cake quickly releases from the pan when flipped. Place a cooling rack on top of the bundt pan and carefully flip the bundt pan over. Give the pan a shake from side to side to gently release the cake from the pan.

Prepare the icing by whisking together the powdered sugar and milk. Slowly add the milk until you reach your desired consistency.120 grams powdered sugar, 15-30 grams milk

Top with a mix of sugar and chopped walnuts if desired.30 grams walnuts, chopped, 15 grams sugar