Chop the ginger, chile, galangal, garlic, lemongrass and onion. Then process all of this together in the food processor to make a bumbu. This is the Indonesian equivalent of what is called curry paste in Thai cooking. For a more traditional approach, you could also use a mortar and pestle.
Season the beef with salt.
Do not shake the coconut milk. Scoop off the thick white coconut cream that floats on top, and put it in a frying pan. Heat the coconut cream until it starts to 'break'. Sear the beef in the coconut cream for a couple of minutes per side. This is just to brown the beef a little; it should remain raw inside.
Take the beef out of the pan and put it on a plate. Do not clean the pan.
Add the bumbu and cook over medium heat, stirring, until the bumbu is golden brown.
Now add the cumin, coriander, cloves, turmeric, and trassi, and stir for another minute.
Add the remaining coconut milk and a tablespoon of sambal oelek and the bay leaf and lime leaf. Bring to a boil and allow to reduce, stirring regularly.
Add the juices that will have leaked from the meat. Keep reducing over medium heat until it's very thick and the color has darkened. This will take about 15 minutes. Turn off the heat and remove the bay leaf and lime leaf.
Cut the beef into cubes. It will still be raw inside. Add the cubed beef to the sauce and stir until the beef is coated with the sauce.
If using a Ziploc bag, you can now put the meat and sauce into a bag and close it with the water displacement method. If using a chamber vacuum sealer, allow meat and sauce to cool off completely before vacuum sealing.
Cook sous vide for 24 hours at 165°F (74°C).
After cooking sous vide, you can chill the bag in ice water and freeze it. If so, simply reheat directly from frozen in the sous vide at 165°F (74°C) for a couple of hours when planning to serve.
To serve, open the bag and strain the juices into a pan using a fine sieve. Reserve the beef.
Bring the juices to a boil and allow to reduce over medium heat.
When the sauce has thickened, season it to taste with kecap manis. There are also recipes that call for adding salt and palm sugar, but using kecap manis instead (of which salt and palm sugar are important ingredients) has two benefits: it adds some more color and it adds some more flavor.
Now add the reserved beef and stir to coat the beef with the sauce. Bring to a boil, then turn off the heat at once.
Serve with white rice and Indonesian green beans.
