Heat the oven to 180 °C and line a 28 cm x 22 cm baking tray with baking paper. Press the paper neatly into the corners so the egg mixture has a smooth, contained surface.

Whisk the eggs, sour cream, and parmesan in a large bowl until fully blended, then season with salt and pepper. The mixture should look even in color with no visible streaks of sour cream.

Pour the egg mixture into the lined tray and bake for 10 minutes. Remove it when the surface is set but still lightly glossy, rather than dry or deeply browned.

Lay a silicone mat over the warm egg sheet, turn it over carefully, and peel away the baking paper. The egg should release in one piece and feel soft enough to bend without cracking.

Return the baking paper to the tray, arrange the cheese over the egg, add the ham, and roll it lengthwise. Keep the seam underneath as you transfer the roll back onto the lined tray.

Bake the rolled omelette for a further 5 minutes, then slice and serve. The cheese should be melted and the roll should have a gentle spring when lightly pressed.

Set the oven to 180 °C and line a 28 cm x 22 cm baking tray with baking paper. Make sure the paper sits flat so the egg layer bakes evenly.

Add the eggs, sour cream, and parmesan to the mixer bowl and mix for 15 sec/speed 5, then season with salt and pepper. The finished mixture should look smooth and uniform.

Spread the egg mixture in the prepared tray and bake for 10 minutes. The center should no longer look wet, though the top should retain a soft sheen.

Cover the hot egg sheet with a silicone mat, invert it carefully, and remove the baking paper. Lift the paper slowly if an edge clings, rather than tugging at the warm eggs.

Put the baking paper back in the tray, cover the egg sheet with cheese and ham, and roll it lengthwise. Set the roll seam-side down to help it hold its shape.

Return the roll to the oven for a further 5 minutes before cutting it into portions. The filling is ready when the cheese has melted through the center.