Coat the bottom of a large skillet with oil, then heat on medium-high. When pan is hot, lay scallops down. Allow bottoms to sear for about 3 minutes, then add butter and rosemary to center.
Flip scallops and baste with rosemary butter for about 2 more minutes. Drizzle over lemon juice, then remove from heat—do not overcook.
In large sauce pan, melt butter on medium heat. When the butter has melted and begins to froth slightly, add shallots and garlic.
Allow aromatics to brown slightly, then add polenta. In order to make the polenta smooth, I used a potato masher to mash the polenta, added an additional cup of water to add moisture and achieve a thick, smooth consistency, and 1/2 tablespoon of chicken bouillon for flavor.
Heat polenta for 5-8 minutes on medium-low heat, then stir in mascarpone and Parmesan until creamy and melted.
Plate the scallops on top of a dollop of polenta. Garnish with fresh thyme, rosemary, and freshly grated lemon zest.