Heat oil into a large saucepan on medium/high heat, then stir-fry curry paste to build aroma.
Add 100ml water to loosen the mix, and then blend in fish sauce, palm sugar and tamarind (optional)
Add beef and coconut milk, bring to a light boil, cover and cook for 30-45 minutes.
Add potatoes, onions and peanuts with remaining water (100ml), bring back to a simmer and cook for a further 30 minutes (uncovered)
Add cherry tomatoes stir well before removing from heat. If the sauce is too thin, continue to simmer to reduce sauce further
Garnish with thinly sliced red chilli just before serving (optional) and serve hot with freshly steamed Thai Jasmine rice