For the Gremolata:
Heat the oil in a wide-based casserole dish
Add garlic, fennel seeds, and chilli flakes. Fry, stirring, on a medium heat for 30 seconds
Add the leeks, fennel, a tsp of Flaky salt.
Partially cover and cook for 10 minutes stirring occasionally
Turn up the heat, remove lid, so the leeks take on colour
scrape the base of the pan using a dash of the vegetable stock
Add the cannellini beans and remaining stock.
Bring to boil, then simmer and cover for 20 minutes, topping up stock if required
Meanwhile, make the gremolata by mixing all the ingredients with a tsp of flaky salt in a pan
Once the beans have had their 20 minutes, stir in the tahini and lemon juice. Add more stock if needed
Season to taste, then serve