In a large pot, melt butter (or heat oil) over medium heat.
Add diced onion and cook until translucent (~3-4 minutes).
Stir in minced garlic and cook for 30 seconds until fragrant.
Pour in vegetable broth and bring to a gentle boil.
Add peas and reduce heat to simmer for 15-20 minutes until peas are tender.
Use an immersion blender to purée until smooth (or transfer to a blender in batches).
For extra creaminess, stir in heavy cream (optional).
Season with salt, pepper, and dried mint (if using).
Garnish with fresh parsley or croutons.