From all the Greek foods that I was cooking as a student, tzatziki is the one that all my international friends loved!
For this simple and easy recipe you will need around 20 minutes of preparation.
Ingredients:
400 gr Greek style yogurt -one medium container (Total if you can find)
1 big cucumber
4 cloves of garlic
2 big spoons of vinegral
1/3 cup of olive oil
1/2 tablespoon of salt

Wash the cucumber very well, cut the edges but do not peel it. The secret in this is to grate the cucumber as it is, in the extra coarse side of the grater so that it keeps some of its natural water content. Then, leave it in the strainer for 10-15 minutes until all the water has drained and finally squeeze out the excess of water with your hands.

Put the yogurt in a big bowl, add the cucumber and mix it very well with a spoon. If you don't find Greek yogurt you might have to strain it seperately before mixing. Grade the garlic in very small pieces and melt it until it becomes creamy, or mince it very fine. Add a bit of salt and mix it with the yogurt. At this step you should taste the yogurt with a small spoon to check how strong it is. If you want it to be stronger, you can add more! Finally, add the oil and the vinegral and keep mixing until it becomes smooth and homogenous.

Tzatziki is served in a bowl as a cold side plate. I add 2 or 3 olive oils at the top for decoration and drizzle some olive oil. It is perfect to eat with chips, pitta bread, steak, lamb...
It is preserved in the fridge and you will notice that the taste gets better the next day!
Avoid eating it in the morning because if it's too strong, the garlic smell might be unpleasant..