Sourdough Blueberry Muffins

Name: Sourdough Blueberry Muffins
Prep time: 25 min
Cook time: 20 min
Total time: 45 min
Cuisine: American
Ingredients: ½ cup (60 grams) all-purpose flour; ¼ cup (50 grams) brown sugar (packed); ¼ cup (20 grams) rolled oats; ¼ teaspoon kosher salt; 4 tablespoons (57 grams) unsalted butter (softened); 1 ½ cups + 1 tablespoon (190 grams) all-purpose flour; 2 teaspoons (8 grams) aluminum-free baking powder; ½ teaspoon kosher salt; ½ cup (113 grams or 1 stick) unsalted butter (melted); ½ cup (100 grams) granulated sugar; 2 large (100 grams) eggs (room temperature); ¾ cup (180 grams) milk (room temperature); ½ cup (100 grams) sourdough starter discard (room temperature); 1 teaspoon vanilla extract; 1 ½ cups (225 grams) blueberries (fresh or frozen (plus more for topping))