Use this recipe to make Chocolate Whoopie Pies with Cassis Filling.
In the bowl of an electric mixer fitted with the paddle attachment, beat together cream cheese and butter on medium speed until mixture is light and fluffy, about 3 minutes. Scrape down bowl with a spatula. Add creme de cassis, food coloring, and salt; mix on low for 30 seconds.
With the mixer on low, slowly add 2 1/2 cups confectioners' sugar; beat for 30 seconds. Scrape down bowl. If consistency is too soft to hold its shape, add additional confectioners' sugar, 1 tablespoon at a time, until desired consistency is reached.
Cassis filling can be kept refrigerated, in an airtight container with plastic wrap pressed on the surface, for up to 5 days.