Start by setting the sous vide cooker to preheat the water at 55°C /131°F. While the water is heating, we'll prep the prime rib.
Start by cleaning and cutting the prime rib. Remove any excess fat or lean parts that are hanging from the prime ribs. We will use these remains to prepare our gravy sauce later, so keep them off to the side.
Let's prep the prime rib with the dry meat rub, paprika, and salt and sugar. Let it sit for about 10-15 minutes, allowing extra juices to settle.
After 15 minutes, put the prime rib inside the bag. Add the rosemary branches and the anise clover. Then add the olive oil.
Seal and place the vacuum bag into the sous vide container. Cook the prime ribs for 15 hours.This will ensure that the bone will get out with ease and the meat will be tender and soft.
In the meantime, we can start to prepare the gravy sauce. We'll need to start by making beef broth using the prime rib remains we set to the side earlier.
Take a large pot, add 600 ml of water, and add the beef remains. Also add in the half onion and a bit of salt.
Let the broth cook for 5 hours.
At this point, we have a meat stock to prepare our gravy sauce. Start with taking the butter and melting it in a small pan over low heat.
Then add the flour and whisk it. This will form the roux, a classic french recipe used to thicken any sauce. Add it to the boiling broth and whisk until it start to thicken.
Season with salt and pepper, and keep by the side. Use it to glaze the prime rib later.
Once the prime ribs are ready, simply take them out of the vacuum bag, dry them out.
Start up the grill and throw the prime rib onto it when the grill is at the highest heat possible. We want the meat to roast and get a good sear all around without cooking any further.
Serve glazed with the gravy sauce. That's it, enjoy!