Separate broccoli into long stalks with florets and peel off any tough skin. In a large pot of vigorously boiling salted water blanch broccoli 4 minutes. Drain and immediately plunge into ice water to refresh.
In a wok heat oil to smoking point. Add broccoli and stir-fry garlic and ginger 2 minutes, until aromatic. Add broccoli, soy sauce, fish sauce, vinegar, chicken stock, sugar and MSG and toss to mix well. Remove from heat. Using a slotted spoon, transfer broccoli to a bowl. To liquid in wok, add sesame oil. Adjust seasoning to taste (you may not need to add much salt) and pour liquid over broccoli. Marinate at least 3 hours before serving. Serve at room temperature.