Thick creamy sauce made with oil and egg yolks

Ingredients:
2 egg yolks
1/2 tsp salt
1/2 tsp sugar
1/2 tsp mustard powder
1 tbsp vinegar
1 1/2 cups salad oil

Method:
1. Beat the egg yolks in a bowl with a whisker for about a minute.
2. Add mustard powder, salt, sugar, 1 tsp vinegar and beat for another minute.
3. Add oil, a little at a time, beating or whisking continuously, until entire oil is used up.
4. In the end add rest of the vinegar, whisk again to mix.