Coarsely grind the peanuts, keep aside.
Dissolve the tamarind paste in 2 tbsp water, keep aside.
Heat 4 tbsp oil in pan, sear the lamb pieces in batches till evenly brown. Keep aside. Fry the baby potatoes and shallots in the same oil. Keep aside.
Pour the coconut milk in a deep bottomed pot, throw in the bay leaves and green cardamom., bring to a gentle simmer. Add the lamb to the pot, let it stew over a low medium flame, about an hour or so.
Crack the coconut cream in a separate hot pan. Add the massaman curry paste to the coconut cream in small increments, cook over a high flame, stirring occasionally, till the curry paste is completely incorporated and oil starts getting released from the paste.
Add the fish sauce, palm sugar (or jaggery) and tamarind water. Give it a hearty stir. Cook for 3-5 minutes.
Now add the paste to the stewing lamb, throw in the potatoes, onions and peanuts, give it a mix.
Add a cup of warm water, continue to cook over a low-medium flame, some 20 minutes or so.
Adjust seasonings. Serve hot.