Southern Indian Crab Curry

Name: Southern Indian Crab Curry
Ingredients: olive oil; 2 heaped teaspoons turmeric; 2 large cloves of garlic peeled and finely sliced; 1 teaspoon cumin seeds; 2/3 fresh red chillies deseeded and finely sliced; 2 heaped teaspoons black mustard seeds; a good bunch of fresh coriander leaves picked; 3 teaspoons fennel seeds; sea salt and freshly ground black pepper; 5 green cardamom pods crushed and husks removed; juice of 2 lemons; 20 g butter; 500 g picked white crabmeat; a thumb sized piece of fresh ginger peeled and finely sliced; 1 x 400ml tin coconut milk; 1 medium white onion peeled and finely sliced; 250 g brown crabmeat