Ingredients :

• Softened butter — Truly soft: your finger should sink in without resistance. If you forgot to take it out of the fridge, a few 10-second pulses in the microwave will do. Cold butter will cause your batter to curdle—you’ll see it and feel it under the whisk.
• Cream cheese — Philadelphia is the most common and works perfectly. No low-fat versions here—the fat is what provides the texture. Take it out of the fridge in advance too; it must be at room temperature before going into the batter.
• Limes — You’ll need 4 to 5 depending on their size. Choose firm limes with shiny skin—soft ones give little zest and bitter juice. Key Limes are smaller and more fragrant if you can find them. Otherwise, classic Persian/Tahiti limes work great.
• Icing sugar (for the glaze) — It dissolves in the lime juice without heat—that’s the advantage of icing sugar. Sift it first if you want a smooth glaze. The ideal consistency: it should drip slowly from the tip of the spoon, neither too liquid nor pasty.