Melt the buttery spread (or normal butter if you're not vegan) in a saucepan and add the chopped onion, leek, celery and salt. Cook the veggies for about 10-15 minutes.
Add the potato, sugar, peas together with 1.25l of water and bring to the boil. Simmer for around 20 minutes, adding the finely chopped lettuce in the final 2 minutes.
Remove from the heat, stir in the soya milk and season to taste. Puree in batches until smooth.
Whizz the garlic, basil and olive oil in a food processor together with a pinch of salt to make the dressing. Set aside.
Ladle the soup into bowls, add a few dots of the green basil oil and scatter the toasted flaked almonds over each.