1/2 teaspoon instant coffee granules or freeze-dried espresso (no, your fudge sauce will not taste like coffee...it will just taste more like chocolate)
1 teaspoon hot water
1 cup chocolate chips (semi-sweet or dark)
1 cup mini marshmallows
1 cup evaporated milk (I use 2% or skim)
1 teaspoon vanilla
Dissolve the coffee or espresso in the hot water in a large (8-cup at least) microwave-safe bowl or in a medium-sized saucepan. Dump in the other ingredients except the vanilla and mix rather halfheartedly. Microwave on high power until thick and bubbly--about 4-6 minutes total, stirring after every minute. This is not the time to walk away unless you're going for the chocolate volcano effect in your microwave. If you're using the stovetop, cook over mediumish heat until bubbly and thick, stirring constantly. (No walking away here, either. Scorched chocolate is a very sad thing.) Once your E.H.F.S. is thick and enticing, stir in the vanilla and cool slightly before serving or storing in a glass jar in the refrigerator. The basic recipe makes about 1 1/2 cups but is easily doubled or tripled. (Or quintupled, if you're making enough for a high school marching band post band-camp ice cream buffet. For instance.)
http://guiltychocoholicmama.blogspot.com/2015/05/a-hot-fudge-emergency.html