Heat oil in large saucepan, cook steak, stirring, over high heat until steak is browned all over.
Remove steak from pan, drain on absorbent paper.
Add potato and onion to same pan, stir over high heat until lightly browned.
Stir in musaman curry paste, stir over heat 1 minute.
Stir in coconut cream, then stir in steak, combined tamarind concentrate, the water and sugar, bring to a boil; reduce heat, simmer uncovered for about 45 minutes or until meat is tender and mixture has thickened.
Musaman Curry Paste: Combine onion, garlic, lemongrass, chilli, seeds, cardamon pods, nutmeg, cloves and peppercorns in a small bowl, sprinkle onto oven tray; bake in moderate oven for 10 minutes, cool.
Blend or process shrimp paste and the water until combined.
Add spice mixture a few spoonfuls at a time; blend or process until finely chopped.