One that I was recently re-introduced to is clarified butter.
Though I learned how to make it in culinary school, it is a bit fussy to keep an eye on when making it on the stovetop. That involves melting the butter in a saucepan and letting the water boil off. You have to be careful though, because on occasion it pops, sending hot butter in the air. It also involves skimming and stirring for several minutes, which seemed like a lot of effort, and sometimes pain, for something that isn't required for a kitchen.
However Cook's Illustrated, plus a few other websites I keep an eye on, came out with an oven method that works remarkably well.
Heat an oven to 250 F. Cut up two to three pounds of unsalted butter in a saucepan or small Dutch oven and cook for two to three hours.
What you are looking for is a clear liquid with solid bits starting to turn brown on the bottom. The solid bits are key, because if they burn they will ruin the butter's flavour.
Strain the mixture through a sieve lined with cheescloth to get rid of solid bits and foam, and pour into a clean glass jar.
Using unsalted butter is better in this case because the salt can contribute some off flavours when cooked, although I have used salted butter and I didn't notice it that much.
Clarifying butter gives it some interesting properties as well.
First off, because there is no water it lasts longer on the shelf. You can keep it out for a few months rather than a few weeks.
Second, it has a higher smoke point at around 485 F. That means you can use it for higher heat applications such as frying without giving your food a burnt flavour.
Third it changes the flavour in a subtle way. You get a vaguely nutty taste to whatever you are adding the butter into.
It does of course up the fat content. Since the extras in butter have been cooked off and strained out, what you are left with is all butterfat.
Clarified butter can be used however you like, but two things have stood out for me so far: popcorn and soup.
You may remember I wrote about sautéing my popcorn last year. Well instead of using oil in the bottom of the pan, use some clarified butter. It can handle the heat of the making popcorn. After making the popcorn melt a little more to drizzle on top if you like a little extra butter flavour (I know I do).
For soups, I use it to sauté the vegetables in first instead of oil or regular butter. It gives the soup a slightly richer flavour overall, without overpowering anything.
Clarified butter isn't going to be a staple of my kitchen anytime soon, however it is a nice treat to have now and then. And sometimes the best flavours are those that you save for special occasions.