Heat the olive oil in a large pot, add the onion, and cook for about 4 minutes until softened.
Stir in the garlic, then add the diced potato and vegetable broth.
Bring the mixture to a boil, reduce the heat, and simmer for about 10 minutes until the potato is tender.
Add the frozen peas and cook for another 4 to 5 minutes without overcooking them.
Stir in the mint and blend the soup until completely smooth.
Allow the soup to cool slightly, then mix in the Greek yogurt and lemon juice.
Season with salt and pepper, then serve warm or refrigerate until chilled.