Marinate the beef:

In a bowl, mix the garum, water, sugar, garlic pulp, and ginger pulp until the sugar is fully dissolved.
Submerge the beef strips in the marinade so they are completely covered.
Tip: For best results, marinate vacuum-sealed in the fridge for at least 1 night and up to 3 days.

Make the glaze:

Remove the beef from the marinade. Pour the marinade into a small saucepan and gently bring it to a boil.
Skim off any foam or impurities. Let it reduce slowly until it becomes a thick, intense glaze.

Prepare the beef:

Pat the beef dry with paper towels.
Lightly brush with sunflower oil.

Grill:

• On the barbecue: Make sure your grill is extremely hot. Briefly sear the beef on all sides so the exterior is cooked, but the interior remains rare. Avoid burning.
• Alternative: Use a heavy, very hot steel pan to quickly sear the beef on all sides.

Finish:

Let the meat rest for a few minutes on a rack. Brush generously with the reduced glaze.

Serve:

Slice thinly and serve immediately.