• Begin by peeling the potatoes and cutting them into thin strips. Peel the onions and slice them thinly, then gently sauté them in a small amount of butter without allowing them to brown.
• Take an ovenproof baking dish and grease it. Start by creating a layer at the bottom with the sliced potatoes. Next, add half of the sautéed onions and half of the sprat (anchovy) fillets. Follow this with another layer of potatoes, and then add the remaining onions and sprats. Finish with a final layer of potatoes, ensuring the surface is even.
• Season the dish by grinding some fresh pepper over the top and lightly sprinkling it with salt. Pour the cream over the layers until it is nearly visible through the potatoes. To enhance the texture and flavor, you can also dot the top with small pats of butter. Optionally, you can add a sprinkling of breadcrumbs for a crispy finish.
• Place the prepared dish in the oven and bake it at 250°C (475°F) for approximately one hour or until it turns golden brown.

Enjoy your meal!