For the soup, heat the butter in a saucepan and gently fry the onion until softened but not coloured. Add the garlic and cook for one minute.
Add the peas and vegetable stock. Bring to the boil, reduce the heat and simmer for 4-5 minutes.
Add the mint and double cream and simmer until slightly thickened.
Pour the mixture into a food processor, season, to taste, with salt and freshly ground black pepper and blend until smooth.
For the toast, heat a griddle pan until hot. Drizzle the bread with olive oil and chargrill on both sides until crisp and toasted.
To serve, place the soup into a bowl with the toast alongside.