Melt butter in a large saucepan or skillet over medium heat.
Add minced garlic to the butter and saute for about 1 minute until fragrant.
Add cream cheese pieces to the pan and whisk as it melts to combine with the butter (mixture will appear separated but whisks into a smooth creamy sauce once the other ingredients are added).
Add heavy cream and whole milk gradually, whisking the sauce at the same time, until smooth.
Add the parmesan cheese by the handful, whisking until melted and combined between each handful of cheese.
Whisk in 1 cup of chicken stock and bring mixture to a simmer.
Add the tortellini to the pan and cook for 5-6 minutes until sauce has thickened slightly and the tortellini is cooked.
Season with salt and pepper to taste, sprinkle with freshly parsley and more grated parmesan, and serve.
Notes
A rich and creamy sauce, but thin enough to coat the tortellini and remain saucy instead of thick and gloppy as the dish cools.High fat levels in the cream cheese and heavy cream help to prevent the sauce from curdling.The chicken stock adds enough liquid to simmer the tortellini right in the sauce, reducing time and dishes to clean. If you are using dry tortellini rather than the fresh, refrigerated kind, you will need to increase cook time and possibly add additional chicken stock.Do not cover the pan when simmering the pasta - the extra liquid will evaporate a bit and help to thicken the sauce.Store in an airtight container in the refrigerator for up to 5 days.