Bring a large pot of generously salted water to a rolling boil.

Add the spaghettini and cook according to package directions until just shy of al dente, as it will finish cooking in the sauce.

Just before draining, reserve about 1 cup (240 ml) of the starchy pasta water. This is the secret to a silky sauce!

Drain the pasta well.

While the pasta cooks, heat the olive oil and optional butter in a large skillet or pan over medium-low heat.

Add the sliced garlic and red pepper flakes.

Cook gently, swirling the pan often, for 3-5 minutes until the garlic is fragrant and just beginning to turn a pale golden color.

Do not let it brown or it will become bitter.

Immediately add the drained pasta to the skillet along with about ½ cup of the reserved pasta water. Increase the heat to medium-high and toss vigorously for 1-2 minutes. The starchy water will emulsify with the oil to create a light, creamy sauce that clings to every strand.

Remove from the heat, stir in the fresh parsley, and toss one last time.

Serve immediately, topped with a generous sprinkle of Parmesan if desired.

Slice your garlic, don't mince it. Thin slices provide a sweeter, more mellow flavor and are far less likely to burn than tiny minced pieces.