If your gelato recipe calls for eggs, the timing of when you add those yolks is important. Once your mixture is simmering, it's go time. But if you add them too quickly or into a mixture that's too hot, you'll end up scrambling those eggs rather than incorporating them into a creamy dessert. To avoid the problem, you need to temper those eggs before adding them into the simmering milk mixture. What does that mean? It's easy -- it's really just a little extra whisking. Place all the yolks your recipe calls for, along with the sugar and salt, in a separate bowl, and while whisking add about 3 to 4 tablespoons of the hot milk mixture to slowly raise the temperature of the eggs. Then, and only then, add the yolk mixture to the hot milk mixture; keep whisking until the milk and yolk mixture reaches about 180 degrees Fahrenheit (82.2 Celsius) [source: Berard].
What'll that look like? You'll want to continue whisking or stirring it until the liquid begins to coat the back of the spoon. This is called a nappe, and it may take anywhere from about five to 10 minutes for your mixture to reach this clingy stage [source: Elizarraras].