RINSE all the lentils, together in fresh water, at least 3 times. Then cover lentils again in fresh water and let soak while you prep the spices + veg.
TOAST the black pepper, coriander, cumin and fennel seeds in a small pan on the stovetop. Then grind together, and pass through a seive (chewy option: you might want to toast the fennel seeds separately and add them whole.)
FRY your onions in 2-3tbs of oil or butter and a few pinches of salt in a soup pot until golden, then add garlic, stir for 2 minutes, then grate your ginger into the pot. Add all the spices(except tumeric) and celery next and stir until celery softens.
ADD the 1 tsp of tumeric, 2 tbs chickpea flour, 2 cups of stock, and 2 cups of water to pot. Set heat on high.
DRAIN lentils from their soaking water, give them one more quick rinse in fresh water, then add to soup pot. Add the chillies and the rest of the veg(except the jalapẽno, if using) salt to taste, and bring to boil, then allow it simmer on med-high until the lentils are tender and toothsome. Stir the soup from time to time to ensure lentils don't stick to the bottom of the pot, adding more fresh water if necessary.
TURN off heat, but leave the pot on the burner. Stir-in coconut milk and jalapẽno, if using.
SQUEEZE the juice of a lemon or lime slice into each serving bowl, garnish with chopped cilantro and some fresh ground pepper.