Heat 2 tablespoons of olive oil in a large pot over medium heat. Add the chopped onion and sauté for about 5 minutes until translucent and slightly golden.

Stir in the fresh or frozen peas to the pot with the onions. Cook them for about 2-3 minutes until bright green.

Pour in 4 cups of vegetable broth and bring the mixture to a boil. Once boiling, reduce the heat to low and let it simmer for 10 minutes.

Stir in a generous handful of fresh mint leaves and remove the pot from the heat. Allow the mixture to cool slightly before blending.

Using an immersion blender, blend the soup until it reaches a smooth, creamy consistency.

Return the blended soup to the pot and stir in ½ cup of buttermilk, or a suitable non-dairy alternative. Season with salt and pepper to taste.

Ladle the soup into bowls, either hot or chilled. Garnish each serving with a squeeze of fresh lemon juice.