2. Step
Add mushrooms to the pan; cook over medium-high heat, stirring occasionally, until golden brown, about 4 minutes. Add shallot, garlic and the remaining 1 tablespoon oil; cook, stirring occasionally, until the shallot is softened, about 3 minutes. Add sherry; cook, stirring constantly and scraping up browned bits from the bottom of the pan, until the liquid is almost completely reduced, about 1 minute. Add soup and water; cook, stirring, until the mixture comes to a simmer. Stir in Worcestershire, mustard and the remaining 1/4 teaspoon pepper.