Put the stock on to heat. Trim and roughly chop the spring onions and add to the stock along with the frozen peas. Bring to the boil.
Remove the asparagus tips and put aside. Roughly chop the stems and add to the saucepan with a pinch of salt. Reduce the heat, cover and simmer for 10–15 minutes, or until the asparagus is tender.
Meanwhile, snip the bacon rashers directly into a frying pan and fry until crisp and golden. Transfer to a plate and put aside.
If there is not enough bacon fat left in the pan for frying, add 1–2 tablespoons vegetable oil and heat. Cut the bread into small dice and fry for 2–3 minutes over high heat, turning the croutons frequently, until golden, then drain on paper towels.
When the peas and asparagus are done, blend the soup to a purée.
Add all but 12 of the reserved asparagus tips to the soup and simmer for about 5 minutes, or until tender.
Pour the soup into four warmed serving bowls. Swirl 2 teaspoons crème fraîche into each and sprinkle with the reserved bacon pieces, the croutons and the remaining asparagus tips. Top with some freshly ground black pepper.