"Singapore Chilli crabs" was the best dish I tasted in Singapore. It is called the unofficial national dish of Singapore. Recently had a craving for this dish and I went looking for crab here in Hyderabad. We dont get the kind of meaty crabs here but then had to make do with what we get here.
Looked online for Singapore Chilli crab recipes and came up with this one which is a mish mash of the different elements from recipes found online

Here is how the original dish looked

and this is how my dish looked

Method

1. Clean and scrub 3 crabs and crack the legs and claws with a spoon so that the masala can seep in. Keep aside
2. Clean and remove the skin of 2 onions and pulse it with 5-6 red chillies to a coarse paste
3. Take 1 tbsp oil in a pan. Fry the onion chilli paste till the raw smell of the onions goes off. I grated in 1 inch of ginger and 5-6 garlic pods too into this onion paste and fried it well till cooked.
4. Add paste of 2 tomatoes along with 1 tbsp tomato  puree or ketchup and saute in the onion mixture. Bring it to a boil.
5. Add 1 tsp white vinegar, 2 tsp light soya sauce, salt to taste, pinch of sugar. I also added 2 sticks of lemon grass for additional flavors. You can add some red chilli sauce too in case you prefer it hot.
6. When the paste is well cooked, add  the crabs and mix well. Add a cup of water to cover the crabs and cover and cook for 15 mins on medium flame. 
7. Beat an egg in a bowl. Now remove the lid of the crab gravy and add the egg with one hand stirring the gravy with the other. Cook for another 5 mins so that the extra water evaporate
8. Garnish with coriander leaves and serve

Here is video of one of the recipes I followed

http://www.sbs.com.au/food/recipes/singapore-chilli-crab

Crabs are my all time favourite. Whenever I have a trip planned to Mumbai, I ask my mom to keep the crab curry ready - that is my sole demand on each of my visit.  Here is my mom's recipe for Kurle Ambat

Method

1. Clean the crabs. I still haven’t mastered this art and get it cleaned from the place where I buy the crabs. I just wash the crabs thoroughly before starting
2. In a small pan take 1 tbsp oil and  roast 1 tsp coriander seeds and 4-5 red chillies. Grind in the mixer with 1 cup freshly desiccated coconut , a pinch of turmeric and 1 marble sized ball of tamarind. Grind this to a fine paste as finer the paste better the taste.
3. In a large pan, add 2 tsp oil.
4. Fry 2 medium sized onions till pink. Now add crabs and sauté for a minute. Add the masala and salt and cook. Crabs take around 15 mins to cook on medium flame. Serve hot with rice.
5. The crabs almost always taste better the next day after absorbing all the masala.

The crab available is Mumbai is much more meatier than the ones available in Hyderabad. I havent verified this personally but it is also said that crabs should be bought when alive as they start losing their body fat and flesh after losing life.

Mud crab that is easily available in Mumbai (http://en.wikipedia.org/wiki/Scylla_serrata)

The blue crab which we get here in Hyderabad (http://en.wikipedia.org/wiki/Crab_fisheries)