Call it whatever you prefer. The concept is simple - marrying fruit juice to sugar and water in such a way that you 1) create a flavored liquid for drink making 2) preserve the fruits flavor for a longer period of time than the juice or the fruit itself can last.
So far I've tested this out with tangerines and Meyer lemons and both really worked out in ways I hadn't quite expected. The cordial helps add body to a cocktail, which is sometimes a weakness of mine, coming up with something that tastes great but has a little more acidity and lightness to it than I'd want (especially in winter). Blood orange is my next test, which would also be a great color to capture.
Use in cocktails at around 0.5 oz to 1 oz, depending on the application and what other fruit you might be using. With a more gentle fruit flavor, you will want to make sure you're pairing it with spirits and liqueurs/modifiers that fit well with the fruit, otherwise you risk losing the flavor profile.
4 parts fruit juice 3 parts sugar
1 part water
Step 1 - Pour your sugar (granulated cane sugar) into a small pot. Pour your water over that. Step 2 - Start stirring as you apply heat. Don't stop stirring much, because you don't want to scorch the sugar. Fully dissolve the sugar. Step 3 - Just as your liquid is about to boil, add your fruit juice.
Step 4 - Continue stirring until the juice is fully incorporated into your sugar syrup.
Step 5 - Let it boil for 30 seconds. This finishes sterilizing your cordial and it also helps clear it up some.
Step 6 - Cool it down to room temperature or lower before using it.
And finally, a little cocktail idea because it worked for both cordials so far.
1.5 oz gin or vodka
0.75 oz cordial (Meyer lemon, tangerine)
0.5 oz lemon or lime juice
0.5 oz St. Germain Elderflower liqueur
2 dashes of Peychaud's
Shake all ingredients together with ice, strain into a cocktail glass. Garnish with a little citrus oil and peel.