Does vodka actually do anything in the sauce?
It can. A little alcohol can help dissolve and carry certain aroma compounds from the tomato and aromatics, which can make the sauce taste a bit more rounded. You simmer it so the sharp edge mellows, but not all alcohol necessarily cooks off.
What if I do not have vodka?
You can skip it. The sauce will still be tasty, just a little less complex. If you want a substitute, use a splash of pasta water plus a squeeze of lemon at the end for a bit of lift.
Can I make it without heavy cream?
Heavy cream gives the most stable, silky sauce. Half-and-half works, but keep the heat lower to prevent splitting. Whole milk is possible in a pinch, but the sauce will be thinner.
Why is my sauce too thick or too thin?
Too thick: add pasta water a tablespoon at a time while tossing. Too thin: simmer 2 to 3 minutes longer, and make sure you used tomato paste (it is the body-builder here).
Why is my sauce grainy?
Usually the Parmesan got too hot. Take the pan off the heat, add a splash of pasta water, and stir gently until it smooths out. Next time, keep the heat low when you add cheese.
Can I add protein?
Absolutely. Crispy pancetta, Italian sausage, rotisserie chicken, or sautéed shrimp all play nice here. Add cooked protein at the end so it stays tender.
Can I use 1 pound of pasta instead of 12 ounces?
Yes. I like 12 oz because it stays extra saucy, but 1 lb works. Plan on a little more pasta water to keep everything glossy.