Different cheeses allow you to tailor the flavor of the puffs to pair with your meal. Use an assertive cheese to get a full flavor, and grate or crumble it so it mixes easily into the dough. In place of the Gruyere cheese, you can use Swiss, sharp Cheddar, Gouda, pepperjack, or even crumbled blue or feta cheese.
Instead of topping the puffs with grated Parmesan, you can use sesame or poppy seeds, or 1 tablespoon of coarse salt.
You can refrigerate the dough (covered) after step 6. Bring dough to room temperature, then proceed from step 7.