If there's one sauce that has a reputation for being difficult, a sauce that strikes fear into the hearts of chefs everywhere, it's Holandase. Now, Holandase, just like mayonnaise, is a fat and water emulsion. Normally, when you mix together fat and water, the fat's going to separate and float on top of the water in a greasy layer. But the key to a successful emulsion is to break that fat up into droplets so tiny that they stay evenly dispersed, causing the liquid to thicken and turn opaque. Traditionally, the way that you do this is by whisking together egg yolks and lemon juice in a double boiler until they're hot and frothy, and then slowly whisking in butter in a thin and steady stream. As you whisk, the butter breaks into minute droplets, while the egg yolk acts as an emulsifier helping to keep those droplets evenly dispersed and thickening the sauce. What you get is a creamy, smooth sauce with a rich texture and mild flavor that's perfect for vegetables, fish, and eggs. But there's a lot of ways it can go wrong. If you don't whisk fast enough, or if you add your butter too fast, the sauce will end up greasy and broken. If you don't cook your eggs enough, it won't thicken properly, but if you cook them too much, you end up with broken scrambled eggs. The fact of the matter is, if you want to learn how to do it the traditional way, the road to perfect Holandase is paved in broken sauces. But here's the good news. There's an alternative method that is completely foolproof, produces a holiday that's every bit as good as the traditional version, and takes about a minute start to finish. All you need is a small pot, a glass measuring cup, and a hand blender with a cup that barely fits a tent. We start by combining an egg yolk, a teaspoon of water, a teaspoon of lemon juice, and a pinch of salt in the bottom of a blender cup. Next, we melt a stick of butter on the stove top until it's completely hot and bubbling. It should register about 220 degrees Fahrenheit with an instant-read thermometer. Pour that butter into a glass measuring cup. Now all we've got to do is stick the hand blender into the cup, start it running, and then slowly drizzle in our butter. Because the hot butter hits the eggs, they start to cook. By the time you've added all of your butter, about 30 seconds later, the eggs are fully cooked, and you've got a smooth, creamy, hot Holandase sauce that is completely indistinguishable from one may of using the traditional whisking method. Holandase is at its best right when you make it, but if you want to store it, your best bet is to keep it in a small, litte pot and a warm spot somewhere near your stove. Just make sure that you use it within a couple of hours. Food lab setting out.