Perhaps they simply realized that this tastes much better than rabbit.
As you can see, there's very little instruction in the recipe. This one is actually quite detailed in comparison to others written down by Great-Grandmother Alice. Basically, I melted everything in a pyrex bowl over a pot of boiling water.
In case you can't read the original, above, here is is again:
1/2 lb. cheese[,] 2 eggs, speck of cayenne[,] 1 tablespoon butter[,] 1/2 teaspoon of salt, teaspoon of mustard[,] 1/2 cup milk[.] [B]reak cheese in small pieces and put it and other ingredients into a saucepan over boiling water stir until the cheese melts serve on toast[.]