1-First Step: Prepare the potatoes and onion. Begin by partially cooking the whole, unpeeled potatoes. Microwave them on high for 1.5 minutes, turn them over, and microwave for an additional 2 minutes, or boil for about 5 minutes until just tender but still firm. Allow potatoes to cool slightly, then peel carefully using a cloth and a knife to avoid burns. Grate the peeled potatoes with a coarse cheese grater, then pat the grated potatoes dry thoroughly using a clean cloth or colander to remove excess moisture. This step is crucial for getting crispy, non-soggy rostis. Finely chop the onion and set it aside.

2-Second Step: Mix the rosti batter. In a mixing bowl, combine the grated potatoes with melted butter, olive oil, salt, pepper, and finely chopped onion. If you find the mixture is too loose or crumbly, add one beaten egg to help bind everything together. Mix gently until ingredients are well incorporated but avoid overmixing, which could make rostis tough.

3-Third Step: Cook the rostis. Heat olive oil in a non-stick or grill pan over medium-high heat. Divide the potato mixture into six equal portions around 1/4 cup each. Lightly pack each portion into a patty approximately 1–2 cm thick. Place the patties in the hot pan, cooking for 1.5 to 2 minutes on each side until golden brown and crisp. If your patties are thicker or your pan requires it, cooking time may extend up to 10 minutes per side. Once cooked, transfer rostis to paper towels to drain excess oil.

4-Fourth Step: Prepare the garnish layers. If using avocado, mash it with lemon juice, salt, and pepper for a creamy layer to add between rostis or on the side. Whip crème fraîche lightly and fold in chopped chives, if preferred, to complement the smoked salmon toppings. Have fresh herbs ready for garnish.

5-Final Step: Assemble and serve. To build the smoked salmon potato rosti stack, place three cooked rostis on each plate stacked neatly. Layer smoked salmon slices between the rostis or atop the stack as preferred. Add dollops of sour cream or crème fraîche (with herbs if used) on the top layer. Garnish with fresh dill or chives. Serve immediately to enjoy the contrast of crispy potato, silky smoked salmon, and creamy topping.