Melt butter in a small saucepan over medium heat. Stir in shallot; cook until shallot has softened and turned translucent, about 3 minutes.
Pour in wine, cream, chicken broth, and lemon juice. Simmer until the liquid has reduced by half, about 10 minutes. Stir in rosemary and season to taste with salt.
Rosemary-Butter Sauce · Dinner Match Lab | Dinner Match Lab