Add the shallots. Cook until softened, about 4-5 minutes. Add the rosemary.
Stir in cream and gently simmer for 5 minutes.
Sprinkle xanthan gum over the top (or stir in the cornstarch slurry). Simmer for 1-2 minutes or until thickened.
Season to taste with kosher salt and black pepper. Serve.
Notes
Storage - This will thicken in the fridge. Just reheat and stir as needed.Thickener - I prefer to use cornstarch. Adding 1 teaspoon of cornstarch will add 2 grams of carbs to the recipe total, which translates to 0.25 grams of carbs per serving.