Wash the leek whites, asparagus, spring onions, and carrots. Trim the asparagus and spring onions, peel the carrots, then cut all vegetables into bite-size pieces.

Heat 2 tablespoons of olive oil in the large saucepan over medium heat. Add the leek whites, carrots, and spring onions, then cook for 5 minutes while stirring.

Add the asparagus and pour in all 250 ml of vegetable broth. Cover the saucepan and simmer the vegetables for 10 minutes.

Add the 3 cod fillets to the simmering vegetables. Cover and gently poach for 8 minutes, until the fish flakes easily.

Transfer the cooked cod fillets to a warm plate. Keep the vegetables and cooking broth in the saucepan over low heat.

Whisk the 2 egg yolks, all 50 g of wheat flour, and the 200 ml of full-fat liquid cream in the mixing bowl until smooth. Ladle in about 60 ml of hot broth while whisking continuously.

Pour the cream mixture into the saucepan and stir constantly over low heat. Cook for 2 minutes until the sauce thickens, without allowing it to boil.

Return the cod fillets to the sauce and warm for 1 minute. Drizzle with the remaining 1 tablespoon of olive oil before serving.