This intensely flavored mousse is made by adding finely grated Parmigiano-Reggiano to gently simmering reduced cream. The mousse holds its shape when cooled, making it perfect for piping. Use any extra to top crackers or vegetables for canapés.
Bring cream to just below a boil in a large saucepan over high. Reduce heat to low. Simmer, stirring often, until reduced by 1/2 cup, about 20 minutes. During last 3 minutes of cooking, whisk in cheese and salt until completely melted and smooth. Transfer mixture to a heatproof bowl, and refrigerate until thickened and cool, about 1 hour. Transfer to a piping bag when ready to use.