Preheat the oven to 425°F (220°C). Position a rack in the middle of the oven so the air circulates evenly around the eggs; high heat gives the whipped whites a quick lift and gentle set while keeping the yolks soft.

Separate the eggs carefully while cold: place the whites in a large clean, dry mixing bowl and the yolks into individual small bowls (keep the yolks whole and covered). Cold eggs separate more cleanly; separating into small bowls protects yolks from breaking and lets you add them later to the baked whites.

Bring the egg whites to room temperature for about 10 minutes (this helps them whip to greater volume). Room-temperature whites trap more air and produce a loftier, silkier cloud than cold whites.

Whip the whites: add a pinch of salt and the optional garlic powder to the whites. Using an electric mixer (hand or stand), beat on medium-high speed until soft peaks form, then increase to high and whip to stiff, glossy peaks. Stiff peaks are necessary so the whites hold their shape in the oven; glossy texture indicates the proteins are well-developed without overbeating.

Fold in the cheeses gently: reserve about 2 tablespoons of the Parmesan for making crisps. Sprinkle the grated Gruyère and the remaining Parmesan over the whipped whites and fold with a rubber spatula in 2–3 gentle turns—you want to keep as much air as possible while distributing the cheese. Overmixing will deflate the clouds.

Prepare the baking sheet: line a rimmed baking sheet with parchment and dot with small bits of butter or brush lightly. The parchment prevents sticking and the butter promotes browning on the undersides of the clouds for flavor.

Mound the clouds: using two large spoons, make four even mounds of the cheese-studded whites on the baking sheet, spacing them at least 2 inches apart. With the back of a spoon, make a shallow well in the center of each mound large enough to hold a yolk. The well gives the yolk a cosy nest so it doesn’t sink during the second bake.

Bake the whites: transfer the sheet to the oven and bake for 3–4 minutes until the exterior of the whites is lightly golden and set but still pillowy. This initial high-heat blast stabilizes the structure and begins to brown the cheese for deeper flavor.

Add the yolks: remove the sheet, carefully spoon one reserved yolk into each well (if any yolks broke, you can brush them decoratively on top). Season each yolk with a small pinch of salt and freshly ground black pepper. This step keeps the yolks tender and prevents overcooking while the whites finish.

Finish baking: return the sheet to the oven and bake 2–3 more minutes for runny yolks (adjust 4–5 minutes for slightly jammy yolks). Watch closely—yolks set quickly and you want a glossy, custardy center.

Make the Parmesan crisps while the eggs finish: on a second small baking sheet or in a small nonstick skillet, sprinkle the reserved Parmesan into four thin 2 1/2–3 inch circles. Bake at the same temperature for 3–5 minutes until golden and lacy, then cool on a rack (they crisp more as they cool). The quick bake concentrates the savory umami of Parmesan and creates a satisfying textural counterpoint.

Plate: transfer two cloud eggs per serving to warm plates using a thin spatula. Top each with a Parmesan crisp, a grind of black pepper, and an optional small pat of butter to melt into the yolk. Serve immediately so the whites remain airy and the yolks run when cut.