Place the bread cubes into a medium mixing bowl, drizzle with olive oil, and sprinkle with garlic powder. Arrange them in an even layer on a baking sheet and sprinkle with some salt.
Place the baking sheet under the broiler and broil until they begin to brown and crisp, about 3-5 minutes, watching closely to avoid burning.
Make the soup:
Coat the bottom of a large pot with olive oil and place it over medium heat. Add the onion and sauté until it's soft and translucent, about 5 minutes. Add the garlic and continue to sauté for about 1 minute more, until very fragrant. Stir in the broth, coconut milk, and peas. Raise the heat and bring the mixture to a boil. Lower the heat and allow to simmer just until the peas are tender, about 5 minutes. Remove from heat and stir in the mint, parsley, and scallions.
Working in batches, transfer the soup to a blender and blend until smooth. Return it to the pot, reheat if needed, and stir in the lemon juice. Season with salt and pepper to taste.
Ladle into bowls and top with the garlic croutons. Serve.
You can substitute frozen peas if you decide to make this when fresh peas aren't in season. Just cut the simmer time down to about 2 minutes.