In an electric mixer/ grinder, add grated coconut, garlic cloves, peppercorns, 1 green chilly, coriander seeds, cumin seeds, turmeric powder. Grind to a smooth paste, initially with 1/2 cup water, pulse everything 2-3 times, then add another 1/2 cup water and grind to a very smooth paste. Arrange a cheesecloth over a strainer ( or simply use a very fine mesh strainer, and skip using the cheesecloth) and a container below, Put this ground mixture over the cheesecloth, squeeze the cloth and collect the extract in a container (This is the thick extract). Put the coconut + spices residue back in the grinder, add another cup of water, grind to a smooth paste, collect the extract in another container (This is the thin extract)
Heat oil in a skillet on medium heat, sauté chopped onions until translucent.
Add shrimps and green chillies, cook until the shrimps are par-cooked and turn opaque about 1-2 minutes.
Add tomatoes, cook until they soften up.
Add the cubed pumpkin, cook, until it softens.
Add the thin coconut milk extract, bring to a boil.
Now, add the thick coconut extract, salt and sugar, mix well and let it simmer for 5-10 minutes. Check for seasoning, adjust accordingly