Slice the peppers in half and remove the stem and seeds. Place them skin side up on a baking pan and press them down with your hand so that they are more or less flat against the pan.
Place the pan under your oven boiler (no need to preheat) and broil for 10 – 15 minutes or until the skins are black and the peppers are soft. When they’re ready, remove to a large container and put on the lid. Leave them to steam and cool for about 10 minutes.
Meanwhile, heat the oil (or water if you are oil free) in a pot over medium-low heat and add the onion. Gently fry until very soft and beginning to turn golden brown. Add the garlic and continue frying until soft and fragrant and the onions are golden brown. You can take your time with this as you’re waiting for the peppers and it’s important that the onions are super soft in order to blend well.
When the peppers are cool enough to handle, peel off the blackened skin. Once the onions are golden brown, add the stock to the pot to heat up.
Transfer the peeled red peppers to a blender along with any juice that they released into the container while steaming and the pan. Blend until broken down. Carefully add the contents of the pot, the salt and continue blending, with the lid slightly ajar to release the steam, until the soup is completely smooth.
If you would like, you can add a bit of lemon juice and vegan cream to the blender. Serve immediately while still hot.