How to Make It
In a spice grinder, combine the coriander and mustard seeds with the peppercorns and summer savory and grind to a powder.
Set a steamer basket in a wide pot and bring 1 inch of water to a simmer. Layer the vegetables in the basket starting with the potatoes, then the carrots, cauliflower and beans. Cover and steam over moderate heat until the beans are just tender, 3 minutes; transfer to a bowl. Steam until the cauliflower is tender, 3 minutes more; add to the bowl. Steam the carrots and potatoes until tender, 10 minutes longer; add to the bowl.
In a large skillet, melt 2 tablespoons of the butter. Add the steamed vegetables and cook over moderately high heat, tossing, until heated through and coated with butter, about 1 minute. Add the lemon juice and season with salt and pepper.
Season the chicken breasts with salt and pepper and coat all over with the ground spices. In another large skillet, melt the remaining 3 tablespoons of butter. Add the chicken breasts skin side down and cook over moderately low heat until the skin is well browned, about 12 minutes. Turn the chicken and cook, basting a few times, until just cooked through, about 7 minutes longer. Transfer the chicken to a platter.
Rewarm the vegetables. Add the chicken stock to the skillet and boil over high heat for 2 minutes, scraping up any browned bits. Add the crème fraîche and bring to a boil, stirring. Remove from the heat and stir in the tarragon. Season the sauce with salt and pepper. Spoon the sauce over the chicken, mound the vegetables alongside and serve.