Why Do Recipes Call for Both Unsalted Butter and, Later, Salt?
Wouldn't it be easier to just call for salted butter?
Recently, someone asked me something that floored me in its simplicity: How come most recipes ask you to use unsalted butter, but then turn right around and also ask you to add salt? Wouldn't it be so much more efficient to simply call for salted butter? I honestly sputtered a little while trying to answer this question. It's one of the brilliant things about talking to folks who are early in their cooking and baking journeys — they dare to fairly inquire about all the pieces of a recipe that I'm simply on autopilot for and never stop to interrogate.
It's a great question, and the answer is all about control. The truth is, most recipes aren't built for efficiency, but to achieve a magical confluence of both being flexible enough for wide us — no matter a person's altitude, kitchen appliances, experience level, or local discrepancies in ingredients — and rigid enough to ensure a consistent result. It's an incredibly difficult thing to pull off.
One of the most useful tools in any recipe developer's pocket is to call for the most basic and unseasoned ingredients so that when combined, they can close the margin of error, and be reasonably sure what the outcome will be. Salted butter is going to be wildly different, in its salinity, all over the world — brand to brand, and farm to farm. Short of asking cooks and bakers to rely on a specific salted butter, which might not be available to them, the only other way to level the playing field in a recipe that does need both solidified fat and sodium is to break each down into component parts — unsalted butter, and later, a dash of salt, often "to taste." Thus, you have the power.
Butter from grass-fed cows tastes very different, more earthy and rich, than butter from cows eating dried hay, and table salt, sea salt, and even Morton's versus Kosher Diamond kosher salt all have very different levels of "saltiness," so there is still a lot of room for variety, but you get to be in control of the end result. That said, if you are intimately familiar with a certain type of salted butter that's available to you, you could, for your own personal efficiency's sake, bake with that. Just be aware that it might take some salty trial and error and may, in the end, not be worth the hassle.