Matt Lewis developed this recipe to turn the Chocolate-Gingerbread Cookies into a deluxe sandwich version. Since the cookies aren't too sweet, the creamy, sugary mascarpone mixture complements them well.
In a bowl, beat the butter until smooth. Beat in the mascarpone cheese until combined. Add the sugar and vanilla and beat until smooth. Refrigerate the filling until it is slightly firm, about 2 hours.
The mascarpone filling can be refrigerated for up to 1 day; let stand at room temperature until softened slightly before using.