Cooking steps:
1. Prepare the base
Preheat the oven to 180 °C. Peel and grate the potatoes finely (or cut them into thin slices). Mix with the egg, grated onion, salt, pepper and a drizzle of olive oil.
2. Bake the base
Spread the mixture on a baking sheet lined with baking paper to form a large, even rectangle. Sprinkle with grated cheese and bake for 25 to 30 minutes, until the top is golden brown.
3. Fill and roll up
Let cool for a few minutes and then spread the cream cheese all over the surface. Place the slices of smoked salmon (or ham) on top. Carefully roll up using the baking paper to form a nice, compact roll.
4. Finish
Put the roll back in the oven for 10 minutes at 180°C to warm it up a bit and make it even more tender. Serve hot or cold, with a squeeze of lemon juice and some fresh parsley.
