5tablespoonscold unsalted butter, cut into small chunks
4tablespoonsgolden brown sugar
Instructions
Set the oven and prepare the pan. Preheat the oven to 375°F, and line muffin pans with paper cups. (You will need about 18.)
Make the batter. In a large mixing bowl, combine the cornmeal, flour, baking powder, 2 teaspoons of the cinnamon, and the salt. Mix until blended. Add the blueberries and chocolate to the bowl and gently toss to be sure they are all coated with the dry ingredients. In another mixing bowl, combine the oil with the sugar, milk, sour cream, vanilla and eggs. Whisk everything together until it's a smooth mixture, about 1 minute.Make a well in the center of the dry ingredients and pour in about half of the wet ingredients. Use a large spoon to fold everything together. Then add the remaining wet ingredients and mix just until everything is evenly blended together. Set aside.
Make topping. In a small bowl, combine the butter, brown sugar and remaining ½ teaspoon of cinnamon and rub it together with your fingertips until it's crumbly. Set aside.
Bake. Fill each paper cup about ¾ of the way up with the batter and then sprinkle each one with the brown sugar mixture, dividing it evenly among the muffins. Bake in the preheated 375°F oven until they no longer look wet and a wooden toothpick inserted into the center of a muffin comes out clean, about 20 minutes.
Cool and serve. Let the muffins cool in the pan on a rack for about 20 minutes. Serve warm or at room temperature.