Place a medium saucepan over medium-low heat. Add the butter and let it melt slowly, making sure it does not brown.
Once the butter is melted, add the minced garlic and stir gently for about 1 minute until fragrant. Be careful not to let the garlic burn.
Pour in the heavy whipping cream and stir to combine with the butter and garlic. Increase the heat slightly to medium.
Let the cream mixture gently simmer for about 5 to 7 minutes, stirring occasionally, until it begins to thicken slightly. You will notice it coats the back of a spoon.
Reduce the heat back to low. Add the freshly grated Parmesan cheese a small handful at a time, stirring constantly after each addition so it melts smoothly into the sauce.
Season the sauce with salt, black pepper, and nutmeg if using. Stir everything together well.
Taste the sauce and adjust seasoning as needed. If the sauce feels too thick, add a small splash of pasta water or cream to loosen it up.
Remove from heat and toss immediately with cooked fettuccine or your pasta of choice. Garnish with fresh parsley and extra Parmesan before serving.
Becky's Tip:
Always use freshly grated Parmesan cheese rather than pre-shredded from a bag — it melts much smoother and gives the sauce a creamier texture without clumping.