i understand your feelings on sandwiches will always be sandwiches and where they come from - but i think you don't read in deep enough.

a sandwich won't immediately become a cake - that's not the way it works. they're too different for that. that's not to say that if you keep changing the sandwich it eventually won't be a sandwich - and whoever came up with confining this to a subway store immediately doomed the analogy. here's a better one:

a restaurant (no specific restaurant) wants to create a great new recipe. the cook starts with a sandwich (original species) and begins serving it to a select group of customers (call this the environment). based on the feedback from those customers (changes in environment/evolutionary pressures) the cook begins tweaking the recipe. he continues the proccess - here changing the meat from sliced ham to ground beef, there adding sauce and mushrooms (microevolution) until eventually he decides that the sandwich filling he has would be better as topping for a pasta. he gets rid of the bread and, after a transitional period, puts it over noodles. by adapting to his customer's demands, the chef came up with an entirely different dish than he started with. there's speciation for you.