Bring 3 quarts water to a boil and add 1 tablespoon salt. One type at a time, blanch the vegetables until barely tender, then remove to a bowl of cold water to stop the cooking. When all are blanched, reserve 1 cup of the cooking water. Drain the vegetables. (This can be done ahead of time.)

In a wide skillet, melt the butter with the thyme sprigs and reserved liquid. Add the vegetables and simmer until they’re warmed through. Add the lemon juice and season with salt and pepper. Add the sorrel and herbs and cook for 1 minute more. Serve at once.