Spaghetti is a straightforward dish almost anyone can make. Boil some pasta, warm some sauce (or make it from scratch), ladle the sauce onto the pasta. That course of action will result in an edible bowl of spaghetti, but it will also leave you with little pools of liquid and a sauce that doesn’t quite cling to your noodles. It’s not the end of the world, but it’s not great.
Thankfully, you only need two things to prevent pooling and help your sauce stick to your pasta—a little bit of butter and some starchy leftover pasta water. Tossing your marinara (or other sauce) and al dente noodles with those two ingredients creates a velvety emulsion that clings to the pasta, permeating it with flavor and preventing those unsightly little pools. You can also use olive oil, but that’s pure liquid fat, and requires far more agitation than the butter, which is a water-in-oil emulsion, with the milk proteins acting as emulsifiers. (I tried a side-by-side comparison of the below method with olive oil, and it came out very watery.)
The order of operations can be tweaked to your liking, but I prefer to add my pasta water to the sauce while it’s still simmering, then gradually it add the sauce—ladle by ladle—to a large pot with the butter and the drained al dente pasta, vigorously tossing after each addition until the pasta is coated with a nice clingy base layer. (This is also how Ralphie from The Sopranos sauces his pasta. Take that how you will.) Next, I add more sauce on top, and that sauce now stays put (until I put it in my mouth). You can also add your noodles, water, and butter directly to the sauce pan, but that hinges on making the exact right amount of sauce for the amount of pasta you cooked, which I am simply not capable of.
This method can be applied to any tomato-based sauce, or any other sauce that doesn’t naturally contain a lot of fat, but I’ll be using a simple store-bought marinara (with a little added wine) as a baseline to give you an idea of the ratios involved. Once you get the hang of it, you probably won’t even need to measure. To make it, you will need:
6 ounces spaghetti (or any other pasta)
2 cups store bought marinara
1/2 cup red wine
2 tablespoons butter
Bring a large pot of salted water to a boil (use the amount of water suggested by the package instructions), and add your pasta. Add the wine and sauce to a sauce pan and bring to a simmer. Let the sauce warm and reduce while the pasta cooks, stirring occasionally to make sure nothing sticks to the bottom. When the pasta is a couple of minutes shy of al dente (refer to the package instructions to get an idea of the time frame involved), carefully remove a cup of the pasta water, then add 1/4 cup of it to the sauce. (Set the extra aside in case you need it later. You can also use it to reheat leftovers.)
When your pasta is close to or at al dente (and there’s a tiny-to-small white dot in the center of the spaghetti strand when you bite into it, depending on how much chew you like in your pasta), cut the heat, drain the pasta, and add your butter to the still-hot pasta pot. Add the noodles and a ladle of sauce, and stir stir stir over the off-but-still-quite-hot burner until the sauce fully coats the pasta. (If you have a gas range, set it to around medium.)
Repeat this with a couple more ladles of sauce until your pasta is as sauced as you like it. You can add all your sauce, or you can add 2-3 ladle’s worth, then serve a little extra on top. If you accidentally over-thicken your sauce, splash in a little bit of that leftover pasta water to loosen things up.
Updated at 3:33 pm EST on 4/8/21 to include a little more info about when to drain your pasta.