Prepare the broad beans, peas, green beans, and snow peas by blanching in boiling salted water until tender. Cool them in ice water, then shell the broad beans.
Peel the turnips, carrots, and white onions, slice thinly, and blanch similarly.
Finely chop the tarragon leaves.
In a sauté pan, melt the butter over medium heat. Add the sliced white onions and cook until lightly golden. Incorporate the other vegetables and simmer for 5-6 minutes. Stir in the tarragon, deglaze with tarragon vinegar, and reduce slightly. Add 20 cl chicken broth and season with Espelette pepper powder, salt, and pepper.
Stir in the cream and simmer briefly to create a light broth.
Divide the vegetables into bowls and spoon the jus over top.
