I usually double this recipe and get about 18 or 20 muffins.
Unlike standard bakery muffins that rely entirely on refined flour for structure, this formula incorporates quick oats. Soaking those oats in buttermilk for fifteen minutes hydrates the starch granules before they enter the oven. Acid from the buttermilk also begins breaking down the oat proteins, yielding a tender crumb rather than a chewy texture.
Overmixing develops excess gluten networks, resulting in dense, rubbery baked goods. Combine the wet and dry components just until flour streaks disappear. Fold frozen or fresh berries in last with a rubber spatula to prevent the pigment from staining the entire batter grey. Distribute the thick mixture evenly into a standard twelve-cup metal tin coated thoroughly with fat.
Baking at a higher temperature of 400 degrees Fahrenheit creates rapid initial steam expansion within the batter. That thermal shock forces the muffins to rise vertically before the structure sets. Monitor the exterior closely after fifteen minutes, removing the tin when the tops spring back instantly under light fingertip pressure.