Heat your oven to 220°C/Fan 200°C/Gas 7. Sift the flour into a large bowl. Scoop out a pinch and sprinkle it over a baking tray. Add 1 level tsp baking powder and a pinch of salt to the bowl. Whisk together. Pour 75ml milk into a jug. Add a squeeze of juice from half the lemon. This will curdle the milk. Crack in the egg. Whisk together.
Pour 3/4 of the liquid into the flour and stir together with a fork to make a soft dough – only add the rest of the liquid if it's too dry to come together. Turn the dough out of the bowl. Pat into a 2cm-high round. Place on the baking tray. Bake for 10 mins, then turn the heat down to 180°C/Fan 160°C/Gas 4. Bake for 25 mins till the bread is golden and it feels light when you pick it up. Cool on a wire rack.
While the bread bakes, pop the haddock in a large pan or wok. Cover with boiling water and put on the lid. Simmer for 5 mins. Drain the haddock into a colander. Wipe the pan clean.
While the haddock simmers, trim the top and bottom off the leek. Halve, rinse out any grit and finely slice it. Peel and finely chop the onion. Trim and finely slice the celery. Peel and dice the potato.
Warm 2 tsp olive oil in the pan. Add the leek, onion, celery and potato. Season. Cover and cook over a medium heat, stirring now and then, for 5 mins till the veg have softened a little.
Crumble the stock cube into the pan. Pour in 500ml boiling water. Cover, bring to the boil, then turn the heat down a little and simmer for 15 mins till the veg are soft.
While the veg simmer, slice any thick cores out of the kale. Finely slice the leaves. After 15 mins, stir the kale into the pan. Flake in the haddock.
Pour 150ml milk into the pan. Simmer for 5 mins to wilt the kale. Taste and season. Ladle the chowder into warm bowls and serve with wedges of the soda bread.