1. In a medium bowl, whisk together brandy and 1/4 cup sugar until sugar is mostly dissolved, about 2 minutes. Add lemon juice, fennel seeds, and pepper; whisk to combine. Add lemon zest and cherries and stir until combined. Refrigerate, covered, 24 hours (or up to 3 days), stirring occasionally.

2. In a small bowl, whisk mascarpone until loose and shiny, about 2 minutes. In a medium bowl, using an electric mixer, beat cream and 2 teaspoons sugar on high until soft peaks form, about 2 minutes. Whisk in vanilla. Fold mascarpone into whipped cream until well combined. Divide cherries and liquid among 4 plates. Serve with mascarpone cream and biscotti.