1. Quarter the potatoes and cook in boiling salted water. Remove them and put them immediately through a potato ricer. 
2. Add the butter; season with salt and nutmeg and blend in the hot milk. 
3. At the end, add the garlic purée and cream, then correct the seasoning; the potatoes should be creamy.
4. While the potatoes are cooking, remove any bones from the salmon; salt it lightly on all sides. 
5. Butter an ovenproof dish. Place the slices of salmon in it side by side and coat with a little butter. Cover the dish tightly and cook the fish on the lowest rack of an oven preheated to 80 °C (150° F) for 10 to 12 minutes depending on the thickness of the slices. 
6. Remove from the oven and let the salmon cool for a few minutes. 
7. Reheat the remaining butter in a skillet until it begins to brown. Season with salt and lemon juice and froth lightly with a whisk. 

Presentation

1. Place the salmon fillets on plates with the garlic mashed potatoes. 
2. Pour the brown butter over top and garnish the mashed potatoes with a spoonful of caviar per serving.