Heat olive oil in a large pot over medium heat. Add onion and cook until softened, about 5 minutes.

Add garlic and cook for 1 minute more.

Add frozen peas and vegetable broth. Bring to a boil, then reduce heat and simmer for 20 minutes.

Carefully blend the soup using an immersion blender or transfer to a regular blender. Blend until smooth.

Stir in lemon juice and coconut milk (if using). Season with salt and pepper to taste.