• In the bowl of a KitchenAid fitted with the paddle attachment, combine the flour, sugars, baking powder, baking soda, cornstarch, ground cinnamon, and salt.
• With the mixer on low to medium speed, add the butter and mix until the mixture resembles coarse sand.
• In a separate bowl, whisk together the oil, eggs, vanilla, buttermilk, and yogurt or sour cream until fully combined.
• With the mixer on low speed, slowly drizzle the wet ingredients into the dry ingredients. Once incorporated, increase the speed to medium and mix until smooth and creamy, scraping down the sides of the bowl halfway through, until no lumps remain.
• Let the batter rest for 20 minutes to 1 hour while preheating the oven to 400°F. This allows the flour to fully hydrate and the gluten to relax, resulting in a better rise and a softer, more tender crumb.
• Line a muffin pan with 10 standard cupcake liners. Fill each liner about ¾ full with batter.
• Bake at 400°F for 7 minutes. Without opening the oven door, reduce the temperature to 350°F and continue baking for an additional 9–10 minutes, or until a toothpick inserted into the center comes out clean.

Cinnamon Sugar Topping

• In a medium to small bowl (think cereal bowl), combine cinnamon and sugar.
• In a microwaveable bowl, melt butter.
• Once the muffins have cooled for about 15 minutes—just enough to handle—brush the tops with melted butter, then dip each muffin into the cinnamon sugar to coat.
I use the help of a spoon too, to make sure I get all of the muffin top covered in cinnamon sugar.
• Store the muffins in an airtight container at room temperature for up to 3–4 days.