1 Bring a pot of salted water to a boil. Peel the asparagus, cut off the woody ends and cut the spears into 4 cm (approximately 1 1/2-inch) long pieces. Place in the pan of boiling water and simmer until tender, about 10 minutes. Remove and drain well. Peel the potatoes, rinse and cut into bite-size pieces. Cook in a pot of boiling salted water until knife-tender, about 15 minutes.
2 Meanwhile, peel the carrots and cut them into sticks. Rinse and peel the peppers. Halve the peppers lengthwise and remove the seeds and white ribs. Rinse the cauliflower and broccoli florets, the peas and the snow peas. Add the vegetables to the pan and cook until al dente. Remove and drain well.
3 In a bowl, whisk together the egg yolk and cream. cream, Stir in a little of the boiling water, then stir it all into the pot with the remaining vegetable cooking liquid. Do not boil!
4 Put the vegetables and the potatoes into the soup, heat it up briefly, season and serve in warmed bowls.