Make the bread the day before. Or buy a crusty bread from the store. It’s up to you. In a medium pot, melt the butter. Whisk in the flour then stir in the milk. Add the cubes of cheese. Keep whisking until all the cheese have melted. (FYI: This is pretty much the base for mac’n'cheese.)
Cut up the bread in cubes. I had a leftover garlic bread so I warmed it up in the oven for 8 minutes then cut that up in cubes too.
Transfer some of the the cheese mixture into the fondue pot.