Ingredients :

• Lemon zest — This is what does all the aromatic work. The juice provides acidity, the zest provides perfume — those oils that slightly tickle the nose when you scrape the skin. Always zest before cutting the lemon; it’s ten times easier. And use untreated lemons if you can, the skin won’t have that waxy taste.
• Freeze-dried blueberries — Not the dried blueberries found in granola — those are too sweet and too soft. Freeze-dried ones crunch under your fingers like blown glass and turn into a fragrant, plum-colored powder. You can find them at specialty stores or easily online. Check the label: the only ingredient should be ‘blueberries’.
• Block cream cheese — Spreadables in a tub are too liquid for a frosting that holds. Get the block; it’s denser. The texture of the finished frosting should be firm but supple, like a thick sour cream — not runny, not brittle.
• Cornstarch — A tablespoon in the dough might seem anecdotal. It’s what gives that specific softness, almost silky under the tooth. Don’t replace it with potato starch, the texture will be different.