How to Make It
In a blender, puree the canned tuna with the chicken stock, mayonnaise, capers, anchovy, cornichons, mustard and white wine vinegar. Season the sauce with salt and pepper.
In a small bowl, toss the bread crumbs, thyme, parsley and 1 tablespoon of the oil; season with salt and pepper. Rub the tuna with 1 tablespoon of oil and sprinkle with the seasoned crumbs.
In a large, nonstick skillet, heat the remaining 2 tablespoons of oil. Add the tuna steaks and cook over high heat, turning once, until golden outside but very rare within, about 5 minutes. Transfer the tuna to a cutting board and cut into 1/2-inch-thick slices.
Spoon the sauce onto plates, top with the sliced tuna; serve.