About an hour before beginning this recipe, bring your buttermilk, eggs, butter, and full-fat Greek yogurt (or sour cream) out of the refrigerator. Place them on your counter so they warm to room temperature.
Bake at 425°F for 5 minutes, then, keeping the muffins in the oven, lower the temperature to 375°F. Continue baking for 12-13 more minutes. Test doneness with a toothpick in the center of a muffin, and if it’s clean, remove the pan from the oven.