Leeks: Put a medium ovenproof pan (about 26cm/10-inch) on the hob on low-medium heat. Add 1 tbsp olive oil and once it heats up, arrange leeks in the pan. Allow them to char gently on both sides. Set aside.
Preheat oven to 200C/390F/Gas6.
Make the bechamel: Dilute miso in a splash of plant milk in a bowl. Heat the remaining olive oil in a medium size saucepan, then add flour. Whisk flour and oil together to form a loose paste. Cook on low heat for a minute whisking frequently. Do not let it brown, we only just want to cook off the ra
Season with salt, pepper, a good grating of nutmeg and thyme leaves. Add a squeeze of lemon (optional). Taste and adjust seasoning, remembering that the leeks go in unseasoned.
Topping: Mix the topping dry ingredients in a bowl, then rub softened butter into them with your fingers.
Assemble and bake: Pour the bechamel into the dish with charred leeks – it should just cover them. Cover the dish with a lid (or tightly with kitchen foil) and bake for 15 mins. After 15 mins, uncover and bake for a further 10-15, then scatter the topping on top and bake for further 5 mins or unti
