1. Whisk together egg yolks and sugar in a 2-qt. heavy saucepan; whisk in tequila.
2. Cook over medium-low heat, whisking constantly, 10 to 15 minutes or until mixture thickens and coats back of a spoon. (Do not boil.)
3. Fill a large bowl with ice. Place saucepan in ice. Let custard stand, stirring occasionally, until chilled (about 30 minutes).
4. Beat 1 cup heavy cream at high speed with an electric mixer until soft peaks form. Fold whipped cream gently into chilled tequila mixture just until blended.
5. Arrange assorted berries in 8 serving dishes, and top evenly with tequila cream. Garnish, if desired. Serve immediately.
*1/2 cup orange juice may be substituted.
Note: To make ahead, cover and chill whipped cream and tequila mixture up to 24 hours.