In a medium Dutch oven, bring broth, 2 tablespoons butter, salt, and pepper to a boil over high heat. Slowly whisk in polenta. Reduce heat to medium-low; cover and cook, whisking occasionally, until tender, about 15 minutes.
Remove from heat; stir in mascarpone, Parmesan, thyme, and remaining 2 tablespoons butter until smooth. Garnish with thyme and Parmesan, if desired.
Notes
Kitchen Tip: It is very important to slowly whisk in the polenta to prevent lumps.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/mascarpone-polenta-recipe/