Remove cloves of roasted garlic from the head and mash with a fork until smooth and pasty. This can also be done in a food processor if you'd like.
In a medium saucepan over MED-LOW heat, add butter and melt.
Pour in heavy whipping cream and roasted garlic paste. Stir and heat to a simmer.
Stir in Parmesan cheese and whisk until smooth.
In a small bowl, combine 1 Tbsp heavy whipping cream and 2 tsp cornstarch (or flour), and whisk until smooth.
Add the cornstarch and heavy cream mixture (it will be a thick paste-like consistency), whisking as you add it to remove any lumps and fully incorporate it into the sauce.
Continue to whisk and simmer until sauce has thickened to a classic cream sauce consistency. This may take a few minutes, or it could happen quicker, it all depends on your stovetop and saucepan.
