Thaw the green beans and cut into about 3-4 cm long

Stir-fry the beans in a pan with oil and a pinch of salt

Peel the sweet potatoes and cut into pieces

In a pot, begin to cook the sweet potatoes in salted water

Cut the onions into slices Add about 3/4 of them (about 150g) to the beans and continue to cook

Peel the potatoes and cut into pieces

When the sweet potatoes are starting to be a bit soft add the potatoes in the pot and continue to boil them (This is because potatoes and sweet potatoes have different cooking times)

When the onions of the step 5 become transparent, add the rest of the onions and cook for about 3-4 minutes

When all the ingredients are cooked, put out the heat Add lemon juice, mustard, mayonnaise and mix them Add salt and pepper to taste and mix all

Here, it's ready !! You can serve it hot or cold.