Clean the crabs and remove the air sacs by lifting the bib on both sides. In a stainless bowl, add the milk and buttermilk and place the crabs in it to coat.
In a bowl, whisk together the flour and salt and pepper, to taste.
In a non-corrosive pan over high heat, add 2 tablespoons of water. Bring to a boil and gradually whisk in the butter, lowering the heat and whisking constantly until all is incorporated. Keep warm.
Bring 4 saucepans of salted water to a boil. Blanche the haricots in one, the favas in another, the peas in a third and asparagus in a fourth. When just cooked, strain the vegetables and add each into separate ice water baths. Strain and reserve the haricots, peas and peel the favas, keeping cool. When favas are cooled, peel outer skin and reserve. Cut the asparagus on the bias.
In a saute pan, add 1 ounce of the butter sauce and over medium heat, add the shallots. Sweat until transparent and add the garlic and cook 1 minute more. Saute the scallions (or pearl onions) and radishes until warmed through. They should still be crisp. Add the blanched favas, haricots verts, peas and roasted scallions or pearl onions and cook a few more minutes. Check salt and pepper and add savory. Keep warm.
Preheat and oven to 375 degrees F.
Remove the soft-shell crabs from the milk mixture and shake off excess. Dip into seasoned flour and shake off any excess.
In a saute pan over medium heat, add the vegetable oil and when hot, add the soft-shells, top down. Saute about 2 minutes until brown and crisp and turn. Place in an oven for 2 to 3 minutes until cooked through. Remove from pan and wipe out, keeping crabs warm. Deglaze with the lemon juice, add the butter sauce, tarragon and chervil; do not boil.
On 4 warm plates, place about 1/2-cup of the vegetable mixture and 1 soft-shell crab, surround with the butter herb sauce.