Cook the rice with 100 ml stock for about 20 minutes. Peel onion and garlic and chop finely. Clean, wash and roughly chop the spinach. Wash fish, sprinkle with half of the lemon juice and salt lightly.
Let it simmer in the remaining stock for about 6 minutes. In the meantime heat up the fat. Sauté onion and garlic cubes until translucent. Add spinach. Steam covered for 3-5 minutes. Add rice. Remove fish from stock and keep warm.
Bring the stock and cream to the boil. Stir in the sauce thickener, bring to the boil again. Season to taste with remaining lemon juice, salt and pepper. Arrange fish and spinach rice with the sauce on a plate. Serve garnished as desired with lemon julienne and lemon balm.