To make Bailey's Irish Cream fudge, combine 1/3 cup of Bailey's Irish Cream and 1 tablespoon of instant coffee granules in a small, microwave-safe bowl. Dissolve the granules, and place 1/3 cup of butter, 1/2 cup of evaporated milk, 3 cups of sugar and one 7-ounce jar of marshmallow cream in a saucepan. Add the Irish cream mixture, one package of vanilla morsels and vanilla extract to taste. Chill the melted mixture in an 8-inch-by-8-inch pan.
Microwave the Irish cream and coffee mixture for 10 seconds to help the coffee granules dissolve. If the butter and sugar mixture becomes too thick, add up to 4 more tablespoons of evaporated milk to thin it out. Substitute butterscotch chips for the vanilla chips if desired. Line the pan with foil before pouring in the fudge to make it easier to remove.
Alternatively, prepare Bailey's Irish Cream fudge by placing 12 ounces of milk chocolate chips and 7 ounces of marshmallow cream in a large bowl. Melt 1/2 cup each of unsalted butter and cream in a large saucepan over medium heat. Boil for three or four minutes, and remove from heat. Stir in 1/4 cup of Bailey's Irish Cream. Pour the hot mixture over the chocolate and marshmallow cream, and beat with an electric mixer for one or two minutes.
Pour the fudge into a parchment-lined 8-inch-by-8-inch pan, and chill for at least four hours. Garnish with melted white chocolate and sprinkles if desired.