Fill a large pot with salted water and bring it to a rolling boil—I use about 1 tbsp of salt per 4 quarts because under-salted pasta water ruins everything that comes next. Drop in the 8 oz spaghetti and cook for 2 minutes less than the box says (usually around 8 minutes for al dente). Why? The pasta will finish cooking in the hot sauce, so you want it to bite back when you taste it.

While pasta cooks, place a large skillet over medium heat and add 2 tbsp butter + 2 tbsp olive oil together—this combination prevents the butter from browning too fast, a mistake I used to make constantly. Once the butter foams slightly, add 4 minced garlic cloves and stir constantly for exactly 90 seconds until you smell that toasted-garlic moment but before it turns brown. That fragrance tells you the garlic's flavor has transferred to the fat.

Pour in 1/2 cup chicken broth first (not the full cup of cream yet) and let it heat for about 2 minutes—this step seasons the sauce base and prevents cream from breaking when it hits the hot pan. I learned this trick from a chef friend who explained that broth raises the pH slightly, which protects the cream proteins from curdling. Stir constantly so nothing sticks to the pan bottom.

Reduce heat to medium-low and add 1 cup heavy cream slowly while whisking constantly—I cannot stress this enough because rushing this step is why cream sauces split. Once it's combined and steaming (not boiling), stir in 1 cup shredded mozzarella and 1/2 cup grated parmesan cheese, a handful at a time, waiting until each addition melts before adding more. This takes about 4-5 minutes total, and the sauce should look glossy and coat the back of a spoon.

Drain the pasta (reserving 1 cup of that starchy pasta water) and add it directly to the skillet with the sauce—toss for about 2 minutes while the pasta finishes cooking in the residual heat. Add pasta water a splash at a time if the sauce looks too thick; you want it to flow slightly around the noodles, not cling heavily. This is where I taste and adjust: more salt, more pepper, more lemon zest based on what's needed.

Remove from heat completely and stir in 1 tbsp lemon zest and 1/4 tsp red pepper flakes (or skip the red pepper entirely for Lily, who prefers hers mild). The lemon zest goes in off-heat because heat cooks out the bright citrus oils before they can flavor the dish. Taste one more time and adjust salt or pepper as needed.

Divide into four bowls and top with 2 tbsp fresh parsley split among servings—I always add the parsley after plating because green herbs wilt into invisibility if they sit in hot sauce for more than a minute or two. Fresh parsley looks intentional and tastes fresh rather than cooked-down and dull.