Bring 3 cups of water to the boil. Add peas, shallots, garlic, and salt to the boiling water and cook for 4-5 minutes until the peas are just tender. Take off the heat, strain the cooking water into a bowl and set aside.
Once cool enough to handle, blend the cooked peas-garlic-shallots along with pesto. Season with salt and black pepper. Pour enough cooking water to bring it to the right consistency and blend until smooth.
Transfer to a clean pot and add the milk/cream is using. Reheat before serving. Can be refrigerated and served cold too.
Notes
* Adapted from Nigella Lawson
Recipe by The Blurry Lime at https://www.theblurrylime.com/appetizers/pea-pesto-soup/