In a large pot, heat oil over medium heat. Add leeks and onion and sauté until soft but not browned, about 5 minutes.
Add in potatoes and water (or broth if using). Stir in vegetable stock powder, onion powder, garlic powder and fresh garlic.
Bring to a boil, then lower heat and simmer for 20–25 minutes, until potatoes are fork-tender.
Stir in frozen peas and allow to soften for a few minutes.
Use an immersion blender (or regular blender in batches) to purée until smooth.
Drizzle with cream if using and season with salt and pepper.
Garnish with chopped chives or green onions if desired.