Set your Sous Vide to 57 degrees Celsius (135 degrees Fahrenheit).

Finely chop your meat with a knife if it's not already minced - you don't need a meat grinder. A knife is just fine. Just chop it over with the knife until you have something that resembles ground meat. Form a patty a little loosely and season with salt and pepper.

Then vacuum seal the patty on the moist/wet setting so it is loosely packed - this way it won't lose its shape. Optionally, place a clean lead weight or a teaspoon in the bag to keep it submerged in the bath.

Then, the patty just needs to go in the bath for an hour and a half.

While the patty is in the bath, you can use the time to make the fried onions and some gravy. Heat 3-4 dl of oil in a deep pan or pot over medium heat. Cut the onions into rings but save some raw onions that you can use in and to garnish your beef sandwich. Put the onions in a bag along with the flour and shake. Then use a sieve to filter out the excess flour.

Now, fry the onions in the pan until they are golden or slightly dark brown. Turn them frequently and keep an eye on them; suddenly it goes quickly, and they shouldn't burn too much, or they'll become bitter. When they're done, remove them with a spoon or a strainer and place them on a thick layer of paper towels to cool.

Now it's time for the sauce, melt 25-30 grams of butter in a pot, heat 4 dl of water in a kettle. When the water boils, mix it with a vegetable bouillon cube. When the butter in the pot has melted, add some thickener and whisk, then add the bouillon while whisking. Season with salt and pepper and use more thickener as needed while stirring. Take the sauce off the heat and reheat it when the patty is almost ready. Here, I would like to add that if you want to do something extra for the sauce, use beef stock instead of water. Unfortunately, there is almost no liquid from the patty after Sous Vide cooking.

10 minutes before the patty is done in the Sous Vide, turn on the oven. With five minutes left, place a cast iron skillet on the stove on maximum heat. When the oven is hot, the patty is done, and the cast iron is very hot, put the burger bun in the oven, take the patty out of the Sous Vide, and pat it dry with paper towels. Put plenty of rapeseed oil or alternatively ghee on the cast iron before placing the patty on it, and sear it for 30-45 seconds per side. Ideally, it should be golden brown on the outside but still perfectly cooked on the inside.

Now, reheat the sauce, take your burger bun out of the oven, and then just build the burger.

I started with beets and raw onions, then the patty, closed the burger, and put plenty of sauce on followed by the fried onions and spring onions.

Enjoy and bon appétit.