Put the minced shallot in a ramekin with the white wine vinegar, and set aside.
Cook the asparagus in a pot of boiling salted water until tender. Lift them out with a spider, drain, and immediately plunge into ice water to cool completely, and drain. Blanch the fava beans for 1 minute in the same boiling water, drain, plunge into ice water, drain, and peel.
Heat a thread of olive oil in a frying pan, and cook the bacon until crisp. Add the peas and favas, pour over the stock, bring to a boil, and cook until just tender, about 2 minutes. Add the asparagus to warm through. Drain the shallot and add it, discarding the vinegar. Add the olive oil, balsamic vinegar, lemon juice, salt, and pepper. Taste and adjust the seasonings. Stir through the tarragon, mint and chives, and serve.