Allow to cool completely before frosting. Frost Between the cake layers and pour a generous amount of the mocha glaze over the top of the cake allowing it to run down the sides.
To make the frosting, combine the mascarpone, cream, Greek yogurt, sugar, salt, and vanilla and beat on medium speed until the mixture becomes thick, about 5 minutes.
Keep warm until ready to use, or let cool to room temperature and store in a container with a tight-fitting lid in the refrigerator for up to 2 weeks. Reheat chilled sauce over very low heat on the stove top or in the microwave until warm enough to pour easily.