Heat the oven to 200°C.
Making the stuffing: Heat half the butter in a large wok or sauté pan. When sizzling, add the spinach and stir fry for about 45 seconds. Take off the heat then drain to remove all the liquid. Dry with kitchen paper.
In the same pan, heat the rest of the butter. Add the shallots and fry for a few minutes, until tender and pale golden. Mix in the raisins and the spinach. Tip into a bowl and sprinkle with salt and pepper. Set aside to cool down.
Cooking the potatoes: Lay the potato and garlic slices into a large roasting tin. Drizzle with olive oil and mix. Sprinkle with salt and pepper then form an even layer. Put in the oven for about 15 minutes.
Making the stuffed salmon: Place a fillet onto a dish or a chopping board. Brush with oil and sprinkle with salt and pepper. Add a few dill sprigs and top with the stuffing. Cover with the second fillet then brush over with oil. Carefully slip 2 lengths of kitchen twine underneath the stuffed salmon and tie them.
Take the potatoes out of the oven. Set the temperature to 230°C. Place the salmon on top of the potatoes and put back in the oven for about 15 to 20 minutes. The salmon should be just cooked and the potatoes golden and crunchy. If the salmon is ready before the potatoes, take out of the oven, cover with tin foil and set aside.
Before serving, pour the sour cream into a bowl then stir in the dill and a pinch of pepper. Tip 1tablespoon of olive oil in a frying pan and heat over high heat. Throw in the spring onions and stir fry for about 2 minutes, until the edges become golden. Place the potatoes onto a warm serving dish, add the spring onions and top with the salmon. Sprinkle with dill sprigs and serve alongside the sour cream dip.