Ingredients

500 ml whole milk

½ onion, peeled and sliced

5 black peppercorns

1 bay leaf

2 fillets of natural smoked haddock, pin-boned and skin on (I recommend Alfred Enderby, from Grimsby, https://alfredenderby.co.uk/)

2 tbsp white wine vinegar

4 large free-range eggs

Small bowl of water with ice cubes

40 g  butter

1 tbsp plain flour

1 tbsp wholegrain mustard

30 g cheddar cheese

Lemon

Salt and pepper

200 g washed baby spinach leaves

Method

1. Pour the milk into a large frying pan, add the sliced onion, bay leaf and peppercorns and bring to a low simmer.
2. Place the haddock, skin-side down, into the milk and simmer for 2 minutes. Turn over carefully and simmer for another 2 minutes.
3. Add the white wine vinegar to a small saucepan of water and bring to a boil. Lower the heat until the water is barely simmering. Crack the eggs into the water (it’s easier if you crack them into a cup first), spaced as far apart as possible, and cook for 5-6 minutes (depending on size).
4. Remove the eggs and place immediately into a bowl of iced water.
5. Remove the haddock out of the milk and set aside on a plate, cover and keep warm in a low temperature oven.
6. Strain the milk into a jug through a sieve, then clean the pan and return it to the heat.
7. Melt 25 g of the butter in the pan, add the flour and cook on a moderate heat, stirring, for 2-3 minutes. Add the reserved milk a little at a time, whisking constantly to remove any lumps. Cook for 3-4 minutes until you have a smooth shiny sauce. Add the mustard and cheese, and stir. If the sauce is too thick, add a little more milk. Check the seasoning and squeeze in some lemon juice.
8. Heat a frying pan until hot, add the last of the butter and the spinach and cook until just wilted. Allow to drain (with the pan at an angle) and then place onto the serving plates.
9. Drop the poached egg back into the pan of simmering water for 20-30 seconds to heat through.
10. Place the cooked haddock on top of the spinach followed by the poached egg, then finish with the mustard sauce over the top.