For what purpose do Ed and Min use "egg cubers" in the novel, Why We Broke Up?

Ed and Min buy several egg cubers, which are kitchen utensils that cut boiled eggs into cubes. They use the egg cubers to build the igloo recipe from the recipe book. This igloo is the recipe inspired by the first movie they saw together, Greta in the Wild. Ed and Min make a practice igloo using the egg cubers as a trial run before they have to make one for the party.