Heat beer in a small saucepan until about half evaporates.
Add half of the onion, garlic, tamarind paste, ginger, soy sauce and maple syrup and cook for another 3-4 minutes.
Reduce heat, add 1 tablespoon vegetable oil and season with a pinch of cayenne pepper. As soon as the marinade has cooled, put the meat in and let it steep for 6 hours (less if the pieces are smaller). Turn the meat regularly in between.
Remove the meat from the marinade, pat dry with paper towels and add salt. Sauté meat in a deep frying pan in hot oil. Turn once and fry until the desired cooking level is reached, wrap in aluminum foil and let rest on a preheated plate for 5 minutes.
Remove the fat from the pan, then sauté the remaining half of the onion in the pan. Sprinkle onion with cane sugar and fry for 1 minute. Then pour in the marinade and bring to a boil together with the remaining onions and sugar.
Gently scrape off any sugar mass that settles to the bottom with a wooden spoon and stir. Cut the meat into strips and serve on a plate with the marinade sauce.
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