Place spinach and cheese in a pot without defrosting. Heat up for about 10 minutes at medium heat and let simmer for 2 minutes. Meanwhile beat the eggs, milk and herbs and season with salt and pepper. Heat 1 teaspoon of oil in a pan. Put half of the egg mixture into the hot pan. Fry for 6-7 minutes, stirring occasionally at first, then let it set and turn.
Keep the omelette warm. Prepare the 2nd omelette in the same way. Spread one half of the omelettes with horseradish, then cover with 3 salmon slices each. Finally add the spinach and fold the omelette. Garnish with parsley