Kahr Saiko Kroeung (Cambodian Sweet Beef)

2 pounds top sirloin, cubed
1-inch piece fresh ginger, peeled, thinly sliced
2 (or more) large dried chillies
3 cloves garlic, finely chopped
1/4 cup finely chopped red onion
1/2 cup water
5 tbs olive oil
3 tbs sugar
1 tbs soy sauce
kosher salt/fresh ground pepper
1 cup homemade chicken stock
1 cup coconut milk
2 tbs tamarind concentrate
brown basmati rice
cilantro
Combine beef with ginger and marinate for an hour or more. Discard ginger.
Puree chillies, garlic and onion together with water. Heat oil in a large pot over medium-high heat. Add chilli puree and cook for 2 minutes. Stir in beef, sugar, soy sauce, salt (or, if you prefer, fish sauce) & pepper and chicken stock. Bring to a boil, then reduce heat and simmer, uncovered, for 40 minutes. Add coconut milk and tamarind concentrate and simmer a further 20 minutes, until sauce is thickened. Adjust seasoning to taste. Serve over brown basmati rice and garnish with cilantro.