Mild provolone, gruyere, and gouda cheeses may all be substituted for fontina, depending on your personal preference and the other ingredients in your dish. Why such a wide range of choices? Because fontina cheese is similarly available in a wide range of flavors and textures. The fontina most commonly found in US markets is Danish fontina, which tends to be mild flavored and somewhat softer than Italian fontina.
Spinach, Cheese, and Bacon Bread Puddings (pictured) is a newer recipe on our site, and it would be great with provolone, gruyere, or gouda.
For more information on ingredient substitutions, see our Ingredient Substitutions guide.