Preheat the oven to 350 degrees F
Start with your wet ingredients: Add your melted butter, eggs, salt, sugar, vanilla, milk and sourdough discard to a large mixing bowl and stir it well with a wooden spoon or whisk. You can also use a stand mixer. Just remember not to overmix your batter.
Next add your dry ingredients: Add the flour, baking powder and baking soda. Use a wooden spoon to mix the flour mixture in. Fold your blueberries into the batter. Do not overmix. Mix until just combined.
Spray your muffin pan with non stick spray, or use muffin liners/ paper liners.
Fill the muffin tins about 2/3 to 3/4 full. Add a couple blueberries to the top if you desire. Another option is to add a spoon full of cream cheese to the top of the muffin batter before baking. This is the way my kids like them.
Bake in the oven for 15-20 minutes or until the tops begins to get golden brown.
Take them out of the oven and let them cool before removing from the muffin tins.
Enjoy!
Store any leftover in a airtight container, or freeze them in a ziplock bag for later! You can reheat them one at a time in the air fryer or let them defrost on their own.