Preparation

• 1
  Put the milk, lemon rind, tarragon, onion and bay lead in a saucepan over a medium heat and bring slowly to a boil. Remove from heat and infuse for 30 minutes
• 2
  Melt the butter in a separate saucepan over a medium heat and stir in flour and mustard powder until smooth
• 3
  Strain the infused milk
• 4
  discard lemon, herbs and onion. Gradually beat the milk into the butter and flour until smooth. Bring slowly to a boil, stirring constantly until thickened
• 5
  Simmer gently for 2 minutes, remove from heat
• 6
  Stir in cheese, cream, nutmeg, salt and pepper. Cover sauce and set aside
• 7
  Lightly grease a large baking fish
• 8
  Bring a large saucepan of salt water to the boil, add spinach and blanch for 30 seconds. Drain and refresh under cold running water. Drain again and pat dry with kitchen paper. Put the spinach in a layer in the base of the dish
• 9
  Wash and dry fish fillets. Season with salt and pepper and roll up. Arrange on top of the spinach and pour over the cheese sauce
• 10
  Bake in a preheated oven, 200 Celsius or 400 Fahrenheit (Gas Mark 6) for 35 minutes until bubbling and golden. Serve immediately with a green salad.
• 11
  <em>Thanks to Choose Wisely for this recipe</em>