In a large measuring cup, whisk together ½ cup milk, ½ cup sour cream, ½ cup canola oil, 1 large egg, and 2 teaspoons vanilla extract until smooth. Set aside.
In a large mixing bowl, whisk together 2 cups flour, ¾ cup granulated sugar, 1 teaspoon baking soda, 2 teaspoons baking powder, and ½ teaspoon kosher salt.
Slowly pour the liquid ingredients into the dry and begin to stir gently, being careful not to overmix. There can even be a streak or two of flour left over.
Cover the batter tightly and refrigerate overnight.
When ready to bake the next morning, preheat oven to 350 degrees and spray a 12-cup muffin tin with baking spray and set aside.
Gently toss 1 cup of mulberries with another tablespoon of flour in a separate bowl. Pour berries into muffin batter, stirring gently until just combined.
Using a large portion scoop, evenly divide the batter among prepared muffin tins. Sprinkle the tops of the muffins generously with Turbinado sugar.
Bake cake in preheated oven for 22 – 25 minutes, or until muffins are tall, golden brown, and the tops spring back when lightly touched.
Remove muffins from oven and cool on wire rack for ten minutes before removing from the pan.