A full description can be found here http://mamasminutia.blogspot.com.au/2012/04/cup-cheese.html
Excerpt from web page:-
Cup Cheese (a.k.a Soda Cheese)
Adapted from a recipe my friend Kathy sent me, as well from the recipes I found in Home Cheese Making by Ricki Carroll and Mennonite Country-Style Recipes by Esther H. Shank
1 gallon raw milk
1 cup buttermilk
½ teaspoon baking soda
3 tablespoons melted butter
1 cup cream
1 egg, beaten
1 teaspoon salt
Pour the milk into a large kettle and heat over medium heat until slightly warm. Remove from the heat and stir in the buttermilk. Lid the pan and set aside until the milk is thick enough to cut with a knife—about 36-48 hours. Skim off the thick sour cream and reserve for some other baking project.
Cut the curds into ½ -inch cubes with a knife. Heat the milk to 115 to 130 degrees, stirring gently. Remove from the heat (or, if you want your curds to be firmer, keep the milk at that temperature for up to an hour) and separate the curds and whey by pouring the mixture into a cheesecloth-lined strainer. (Reserve the whey for other baking projects.) Tie up the corners of the cheesecloth and let the curds drain for 8 hours or overnight.
Dump the curds into a bowl and mix in the baking soda and melted butter. Let sit at room temperature for 4-5 hours.
Put the curds into the top part of a double boiler (I set a smaller kettle inside a larger one), making sure the top part is not touching the boiling water. Melt the curds, stirring occasionally. Once the curds are melted (they’ll be creamy-smooth and stringy, like melted marshmallows), add the beaten egg, cream, and salt. Bring the cheese to a boil (mine never got there—I just cooked it for awhile) and pour into dishes. Cover and refrigerate. Serve with crackers, bread, etc.