In the bowl of a stand mixer or a large bowl, mix together the water, all-purpose flour, whole wheat flour, and sourdough starter discard to create the overnight sponge with a paddle attachment or with a large spoon if you're mixing by hand.

Cover the large bowl with plastic wrap, a new plastic shower cap, or a large plate and let it sit out overnight or 6 to 12 hours at room temperature.

The next day (or after the 6 to 12 hours), the sponge will have a fluffy texture and is ready to prepare with the remaining ingredients and it's time to preheat your oven to 400 degrees F. If you're using coconut oil or melted butter, melt that first so it has time to cool down. Scrape the melted oil or butter with a spatula into a heat safe carafe or bowl to help it cool down faster.

Add the milk, eggs, sugar, vanilla, and other dry ingredients directly to the sponge.

Begin to mix in order to break the sponge apart. Make sure to mix well and scrape the bottom of the bowl, turning the batter over to make sure the sponge gets mixed well. Once the oil or butter have cooled, stir it into the muffin batter until fully incorporated.

By this time your oven should be preheated and ready to bake!

Line a muffin pan with parchment paper muffin liners or rub the inside of each cup with oil.

Then, use a 1/4 cup scoop to spoon muffin batter into the prepared muffin cups. I like using this 1/4-cup Stainless Steel Cookie Scoop for scooping and pouring out the batter easily with minimal mess.

Fill the cups 2/3 to 3/4 full (3/4 full will make them more likely to rise over the cup to create that mushroom type top).

Place in the preheated oven to bake for 16 to 18 minutes until a toothpick inserted into the center of one comes out clean. The edges around the top of each muffin should be golden brown.

Let them cool for 10 minutes in the pan and then move them to a wire rack to cool completely.

Serve warm or store for later after they have cooled.