How can I fix my caramel sauce?

Okay. Yes you can save your sauce if it's crystallized without seriously impacting flavor. You can always start over with sugar, so to speak. Unless you burn the whole dang pot, candy can always be saved.

First of all, take your caramel (assuming you've tasted it and it tastes okay) and put it back in a pot with a fair amount of water. How much isn't important really because you'll be boiling it all off. But you do need enough to dissolve everything, and get all those wannabe fudge crystals back in solution. It will take some time to boil off and because of the butter and milk in there you will want to stir occasionally to make sure it doesn't burn. Because burning is the only real way to ruin things.

Stirring can indeed cause crystallization, but its not instantaneous and frankly it's... Not even a problem? I made walnut caramels for Christmas and they all decided to crystallize and turn into fudge after a couple days. They're still delicious. So there is literally no reason to throw away a batch of candy that's crystallized. Even if you can't turn it into what you wanted, it's still good stuff that's nicer than what you'll get at a store. (I am hurt by how many stories I hear of "ruined" candy being thrown out.)

But how do you keep crystallization from happening here? There are several methods to help prevent crystallization. People attach supernatural importance to "not stirring" but... I stir my caramels a lot and don't get crystallization. Stirring won't help you as much as reducing the heat and rotating your pot to prevent hot burny spots, but if it's stir or burn, stir, friend. Stir with my blessing.

That said, the more reliable method to prevent crystallization (where I am) is to add some corn syrup. Literally just add a tablespoon or two of corn syrup to your new pot of dissolved caramel liquid, cook it up to the consistency you want, and you probably won't get crystals again.

You can use any inverted sugar syrup in place of corn syrup though. So glucose syrup and rice syrup and golden syrup and honey (and more) would all work to keep it from crystallizing, but they all have their own character both texturally and flavor wise, so you might want to play around. Honey might be the best texturally, but has a pronounced flavor. Corn syrup is second best texturally in my opinion, but has a very mild flavor. Rice syrup has a lovely maltiness but tends to be stiff and stretchy.... So, playing around is a good idea here.

You could also add a little acid to the mix, but I would say maybe a teaspoon of lemon or preferably a pinch of cream of tartar. You will taste the addition of acid, but in a small enough amount, it would add a tang reminiscent of dulce de leche. Just be careful since you won't be able to take the acid back out.

The other thing I would emphasize is not to heat too high. Use the pot with the thickest bottom you have to try and prevent hot spots, and be willing to use a lower heat and take more time. If you have a glass top stove, you may well have more trouble with crystallization because the glass top doesn't actually keep a good steady heat. A coil top stove or open flame are both better if they're an option, but you'll probably want to stay on low or medium low heat with them. If you use a lower temperature, you'll be able to avoid stirring as well, for any good that actually does.

In short: you can always fix candy. Adding some corn syrup helps prevent crystallization. Acid does too but affects the flavor more obviously. Use a lower heat to prevent hot spots and avoid stirring if you can. If it's stir or burn, just stir. Haters gonna hate. If it stubbornly insists on crystallizing, so what? Let it be fudgey. Dissolve it in coffee. It's still good.

You might be able to save the sauce if you continue to heat it on low to medium heat, but I'm going out on a limb here. It will eventually turn into hard toffee, which you can let cool and eat as it is, or if you need a "sauce" you can process the toffee to a powder and mix it with whipped cream.

My recipe called for a cup of sugar 6 tbsp. of butter and a half cup of heavy cream. My sugar turned into a mess while heating on medium heat. It never melted but seized into little chunks. Then I began adding my butter and it got worse. I took it all out of the pot and added a splash of water to the pot first and let it heat up and put the chunky little bits back in the pot and let it boil for a few minutes. I added half of the heavy cream and it began to smooth out. It was still somewhat grainy so I poured it through a sieve. Voila. It worked fine. I have smooth caramel sauce. Just plain water did the trick.

I don't think you can fix it because you would have to liquify the sugar to correct it. And the butter/milk would burn at those temperatures.

The only caramel sauce recipe I know is:

1. Boil sugar with a little water until brown
2. Pour in a splash of cream (which stops the cooking) and whisk until dissolved.

If I were you I would strain what you have, and use the liquid to make hot chocolate or something. Then start again. Maybe use my recipe, if yours is very different?

The "grainy" look I guess would be crystallisation, which has a couple of causes when making caramel sauce. The recipe you are using is new to me (gee there are a lot of recipes for caramel sauce), the biggest difference being lack of water to sugar (or in another way, too much sugar to water ) for the dissolved sugar to stay "invert." Total cooking time is also a factor.

I suggest you could bring your "grainy" mixture to a simmer and add quarter cup of lemon juice, mix slowly by moving the saucepan around from side to side, front and back. Do this carefully — caramel can cause awful burns, and using a spoon or whisk will cause crystals to form. This should cause "invert" sugar to occur and remain stable — but not for long, perhaps a few hours.