Bo Xao Sa Ot (Vietnamese Lemongrass Chili Beef, 48g Protein)

Jump to recipe ↓

Bo xao sa ot is Vietnamese beef stir fried with lemongrass and chili, and it is one of the fastest ways I know to put 48g of protein on a plate. A pound and a half of flank steak, sliced thin, feeds three people generously, and the whole thing is in the pan for about 12 minutes. The lemongrass does the heavy lifting: it is fresh and sharp and a little citrusy, and it makes lean beef taste like it has been marinating all day when it has really had 20 minutes.

The sauce is barely a sauce. Fish sauce, sugar, garlic, black pepper, the juices from the beef reduced down into a glaze. There is no cornstarch slurry, no stock, nothing to thicken. That is the point. Compared with something like black pepper beef, which is glossy and saucy, this eats drier and more intense, closer to a grilled dish than a takeout one.

If you already make my grilled lemongrass chicken, the marinade will look familiar. This is the weeknight skillet cousin, and it reheats better.

Why this works

The technique is the same one that makes bo luc lac work: a very hot pan, meat in a single layer, and patience for the first minute. Flank steak sliced 1/8 inch thick cooks in about two minutes total, and most of that time should be spent not touching it. If you stir from the start, the slices steam in their own juice and turn grey. Let them sit until the underside is properly brown, then toss once, then out of the pan. Two batches, always. A 12 inch skillet fits about 12 oz of sliced beef in one layer and not more.

The teaspoon of cornstarch in the marinade is not there to thicken anything. It forms a thin coating on the beef that holds moisture in during the sear and helps the fish sauce and lemongrass stick instead of falling off in the pan. It is a much lighter version of Chinese velveting, and on a lean cut like flank it makes a real difference to how tender the result is.

Fresh lemongrass goes in twice. Most of it in the marinade, where it seasons the meat, and a spoonful into the hot pan at the end, where it hits the oil and blooms. The second addition is what gives the dish its smell. Skip it and the flavor is flatter than it should be.

Ingredient notes

Flank steak is the right cut here: lean, big grain, easy to slice thin, and about 21g of protein per 100g raw. Skirt steak works and is a bit fattier. Sirloin or top round are fine if that is what you have, just slice them thinner because they are less forgiving when overcooked. Whatever you use, slice across the grain. On flank the grain runs the length of the steak, so cut the steak lengthwise into two or three strips first, then slice each strip crosswise.

Lemongrass needs to be fresh, not the paste in a tube and not dried. Most US supermarkets carry it now, and any Asian grocer has it. Cut off the root end and the top two thirds of the stalk (that woody part is good for stock or tea, not for eating), peel away the outer layers until you reach the pale, tender core, then mince it as fine as you can. Three stalks gives roughly 4 tbsp. If your knife work is rough, pulse it in a small food processor. Coarse lemongrass is unpleasant to chew.

Fish sauce is the only salt in the dish, so use a decent one. Red Boat, Three Crabs and Squid brand are all good and all available online. Two tablespoons sounds like a lot but it is seasoning a pound and a half of meat. Taste at the end and add more if it is flat.

Chilies are to taste. Two bird’s eye chilies make this properly hot. Two Fresnos make it mild with a bit of warmth. If you are cooking for people who cannot take heat, leave them out of the pan and put sliced chili on the table.

The vegetables are there for contrast, not bulk. Onion and red bell pepper are the classic pairing. Some versions use only onion, and you could add a handful of green beans or sliced celery if you want more on the plate.

Bo Xao Sa Ot (Vietnamese Lemongrass Chili Beef)

Thin slices of flank steak marinated briefly in fish sauce, garlic and a lot of minced lemongrass, then seared hard in batches and tossed with onion, red pepper and fresh chili. 48g of protein per serving. The 20 minute marinade fits inside the prep time.

Print Recipe Pin Recipe

Prep Time 25 minutes mins

Cook Time 12 minutes mins

Total Time 37 minutes mins

Servings: 3 servings

Calories: 550

Ingredients Method

Ingredients

  

• 1.5 lb flank steak 680g, sliced 1/8 inch thick against the grain
• 3 stalks lemongrass tender inner core only, minced very fine, about 4 tbsp
• 5 cloves garlic minced
• 2 tbsp fish sauce Red Boat, Three Crabs or Squid brand
• 1 tbsp sugar
• 1 tsp cornstarch
• 1/2 tsp black pepper coarsely ground
• 2 red chilies Thai bird's eye or Fresno, thinly sliced, to taste
• 1 yellow onion medium, cut into thin wedges
• 1 red bell pepper cut into thin strips
• 1.5 tbsp neutral oil canola, avocado or grapeseed, divided
• 1 tbsp lime juice fresh
• 1/4 cup cilantro roughly torn, to finish

Method

 

1. Slice the flank steak across the grain into strips about 1/8 inch thick. If the steak is wide, cut it lengthwise into two or three long pieces first so the slices are bite sized. Firming the meat in the freezer for 20 minutes makes this much easier.
2. In a bowl, mix the sliced beef with 3 tbsp of the minced lemongrass, the garlic, fish sauce, sugar, cornstarch and black pepper. Toss well with your hands so every slice is coated. Leave at room temperature for 20 minutes while you cut the vegetables.
3. Heat 1 tbsp of the oil in a 12 inch skillet or wok over high heat until it just starts to smoke. Add half the beef in a single layer, spread out, and leave it alone for 60 to 90 seconds until the underside is browned. Toss and cook another 30 seconds, then tip onto a plate. Wipe out any burnt bits and repeat with the second half of the beef.
4. Add the remaining 1/2 tbsp oil to the pan, then the onion wedges and bell pepper. Stir fry over high heat for 2 minutes until the edges char but the onion still has some bite.
5. Add the remaining 1 tbsp lemongrass and the sliced chilies and stir for 30 seconds until fragrant.
6. Return the beef and any juices on the plate to the pan. Toss everything together over high heat for 1 minute so the juices reduce into a thin glaze that clings to the meat. Turn off the heat, add the lime juice, taste and add a splash more fish sauce if it needs salt.
7. Top with the cilantro and serve straight away with jasmine rice, or portion into containers for the week.

Tips and storage

This is a good meal prep beef because the glaze is thin and the meat does not go soggy. Portion it over jasmine rice with a wedge of cucumber or some pickled carrot on the side and it holds four days in the fridge. Reheat in a skillet over medium high heat for two minutes rather than the microwave if you can; the beef stays chewy in a good way and the onion crisps up again. Microwaved is fine too, just cover it and do not overdo it.

It freezes well raw in the marinade. Slice the beef, mix it with the marinade, flatten it in a freezer bag and freeze for up to two months. Thaw overnight in the fridge and cook as written. I would not freeze the cooked dish, since the onion and pepper go limp.

Do all the slicing and mincing before the pan goes on. From the moment the oil smokes to the moment the dish is done is about six minutes, and there is no time to cut a pepper in the middle of it.

For a lower fat plate, trim any visible fat from the flank before slicing and drop the oil to 1 tbsp total. The nutrition numbers assume an untrimmed flank and the full 1.5 tbsp of oil.