Crush the coriander and cumin seeds in a pestle & mortar or high speed mini blender. Combine the rest of the spices and set aside. (you'll have enough for several more dishes).
Place the saffron in a small cup, crush with the top of a wooden spoon then add 1 tablespoon of warm water. Leave to steep for 10 minutes.
Clean the mussels and remove the barnacles and beards. Tap the mussels, discard any that remain open and don’t close.
On a medium heat, add the oil and sweat the shallot until soft and translucent.
Add the garlic and curry spice blend, cook for 1-2 minutes to release the flavour or the spices.
Add the brandy and simmer until it has reduced and become a paste.
Add the saffron water and stir and heat on low for a minute or 2. Set aside.
Heat a separate large saucepan, add the wine, mussels and chilli if using, cover with the lid. Cook the mussels over high heat for about 5 minutes, shaking the pan occasionally until the mussels have opened.
Strain the mussels over a bowl and reserve the liquor. Discard any mussels that didn’t open and put the remainder back in the saucepan and cover to keep warm.
Strain the mussel liquor through a fine sieve to remove any sand.
Reheat the onion and saffron over medium heat. Add the mussel liquor and stir to combine.
Mix the cornflour with 2 tablespoons of cold water. Bring the liquor to a simmer for 3-5 minutes. Add the creme fraîche and cornflour, whisk together with a balloon whisk, then simmer for 5 mins or until the sauce has thickened a little.
(if you prefer not to thicken the liquor with cornflour, just leave it out and reduce the liquor a little more). Check the seasoning ,add salt and pepper if needed. Stir in the parsley.
Place the mussels in 2 bowls, pour over the liquor, add lemon wedges and serve immediately with bread or fries.