Save leftover blue cheese salad dressing for beef sandwiches and Italian subs.
Preheat the oven to 400°. Line a small baking sheet with foil for the croutons.
Tear the bread into bite-size pieces. In a medium skillet, heat the EVOO, two turns of the pan, over medium. Add the butter to the skillet. When it melts, add the bread and toss to coat. Season with salt and pepper and arrange the bread in a single layer on the baking sheet. Bake until golden, 10 to 15 minutes.
In a food processor, blend the dressing ingredients until smooth. Transfer to a squirt bottle or a jar with a lid. (The dressing will keep for about 10 days in the refrigerator.)
Heat a large cast-iron or nonstick skillet over medium-high.
Season the chicken with salt and pepper, drizzle with EVOO, then sprinkle with sage and garlic. Wrap each chicken thigh with 2 slices of speck, layering to cover the chicken.
In a large bowl, toss the greens and half the croutons. In a small bowl, toss the apple with the juice of half a lemon. Add the apple, celery tops and parsley, fennel, and onion to the large bowl. Toss with some of the dressing.
Add 2 tbsp. EVOO to the skillet, two turns of the pan. Add the chicken and cook until cooked through, about 4 minutes on each side. Add the vermouth and stock. Cook until slightly reduced, about 2 minutes. Stir in the juice of the remaining lemon half and the butter to create the sauce.
Divide the chicken among 4 plates. Top with the sauce. Serve the salad alongside.