Heat cooking oil over medium heat in a big pot. Cook onions for 2 minutes. Stir regularly.
Cook buckwheat according to the instruction on the package.
Add garlic, bell pepper, and chili pepper. Cook for 3 minutes more. Stir regularly.
Add celery, zucchini, and carrots cook for 5 minutes more. Stir regularly.
Add tomatoes, coconut milk, paprika powder, pepper, and salt. cook for 10 minutes. Sir occasionally.
Add prawns and cook for another 5 min. Sir occasionally.
Remove from heat. Add chopped parsley if using.
Add shrimps stew to a plate and serve with buckwheat.