1 - Rinse beef with cold water, let it drain off. Cut into thin slices
2 - Peel garlic, scallion and mince them together
3 - Mix beef with fish sauce, minced dry onion, sugar and tapioca starch
4 - Peel pineapple, remove its eyes, cut in quarters, remove its core and then cut into 0.5 centimeter slices
5 - Dissolve tapioca starch and sugar with water in a bowl
6 - Pour cooking oil into a pan; stir minced garlic and dry onion until aroma emerges. Put beef in, stir-fry over high heat, when it is almost cooked, ladle out into a plate.
7 - Pour some more cooking oil in, stir-fry pineapple. Pour the mixture of sugar and tapioca starch in, stir regularly, season with salt. Add beef and stir-fry together.
8 - Ladle out into a plate, spread ground black pepper, coriander on the surface.