Combine 2 tablespoons olive oil in a bowl with 1 crushed garlic clove and thyme leaves. Season the chicken breasts and coat in garlic oil. Wrap each chicken breast with 3 slices of pancetta, slightly overlapping. Enclose chicken in plastic wrap and chill for 2-3 hours.
Preheat oven to 190°C. Break bread into rough pieces and toss in 1 tablespoon oil. Place on a baking tray in a single layer and cook for 10 minutes or until golden and crisp. Cool slightly then place in the bowl of a food processor with lemon zest, parsley and remaining 2 garlic cloves. Pulse until coarse crumbs and season.
Heat remaining 1 tablespoon oil in an ovenproof frypan over medium-high heat. Remove chicken from plastic wrap and cook, turning, for 2-3 minutes until browned all over, then cook in the oven for 10-12 minutes or until chicken is cooked through. Remove from oven, add butter to pan and baste chicken with melted butter. Remove chicken from pan and cover with foil while you make the gravy.
Return frypan to medium heat and cook flour, stirring, for 1 minute until lightly browned. Add wine and cook for 2-3 minutes, then add consomme. Bring to a simmer and cook for 5 minutes until the gravy is thickened. Add sherry to taste. Slice chicken and serve with gravy and green beans scattered with breadcrumbs.