Achieving a smooth and creamy Diplomat Cream is fundamental for the success of your Kiwi Gold Tartelettes. Start by whisking the egg yolks, sugar, and cornstarch together until well combined. The key is to temper the egg mixture by slowly adding the heated milk while constantly stirring to prevent the eggs from cooking too quickly, which can lead to a grainy texture. Once returned to the heat, continuously stir the mixture until it thickens; it should reach a custard-like consistency without boiling. After removing it from the heat, incorporating a splash of vanilla enhances flavor, while allowing it to cool completely is essential. Once cooled, avoid over-whipping the heavy cream, as stiff peaks should be softly folded into the custard to maintain lightness. Following these steps ensures a decadent and silky Diplomat Cream for your tartelettes.