Ingredients :

• Sour cream or full-fat Greek yogurt — This is the ingredient that makes the difference between a dry donut and a moist one. It adds moisture without making the crumb heavy. Use full-fat Greek yogurt — not 0%, which results in a drier texture. In a pinch, heavy crème fraîche also works.
• Nutmeg — A very small amount, but essential. It gives that recognizable ‘bakery’ taste that you can’t quite name. Grate it fresh if you can — pre-packaged ground nutmeg quickly loses its intensity.
• Brown sugar — No white sugar here. Brown sugar keeps the crumb moist for longer and adds a subtle caramel note. Pack the measurement into the spoon before leveling it off.
• Melted butter — For the batter, it should be melted and cooled to room temperature — not hot, or it might cook the egg along the way. For the glaze, it provides that characteristic semi-set texture. No margarine.