Ingredients

Step by step

1. Put the smoked cod loins in a large saucepan and pour over the milk. Set over a medium heat and bring to a gentle simmer, then reduce the heat to low, cover with a lid and leave to poach for 5 minutes, until the fish starts to flake. Lift the fish out of the milk with a slotted spoon, then set aside on a plate. Measure out 375ml of the milk (reserve the rest for glazing).
2. Meanwhile, melt the butter in a separate large saucepan or sauté pan. Add the leeks and cook for 5 minutes until softened. Stir in the flour and cook out for 1-2 minutes. Gradually pour in the poaching milk, stirring constantly. Cook for a few minutes, stirring, until thickened. Remove from the heat, stir in the tarragon and lemon zest, then season to taste. Flake the cod into large chunks and gently stir into the sauce. Spoon into a medium oven dish (we used a 23cm diameter round dish) and set aside.
3. Preheat the oven to 200°C, fan 180°C, gas 6. For the cobbler topping, mix the flour, baking powder and salt in a mixing bowl. Rub in the butter with your fingertips until the mixture resembles breadcrumbs, then stir in the cheese. Mix together the mustard and 3 tablespoons of milk, then mix into the bowl with a cutlery knife, and then your hands, bringing everything into a soft ball of dough. Roll out on a lightly floured surface to about 1.5cm thick. Cut into 8 rounds using a 6cm cutter, re-rolling as needed. Arrange on top of the fish filling and brush with the reserved poaching milk.
4. Bake for 20 minutes, or until puffed and golden. Serve with greens, if you like.