Grate cheddar cheese using a box grater and set aside.
In a small, heavy-bottomed pot, bring chicken broth and cornstarch to a boil. Slowly whisk in grated cheese bit by bit until all of it has been incorporated and a thick, smooth sauce has formed.
Remove from heat and serve immediately with any desired dipping ingredients.
Notes
If you notice your fondue happens to be separating, try reheating while whisking. If this doesn't seem to be doing anything, add in a little more cornstarch dissolved in a touch of cold water. Continue heating and mixing and this should correct it and bring it back to all its smooth and creamy glory.