Chicken Phyllo Bundles
Preheat oven to 350ºF (180ºC).
With sharp knife held horizontally, cut chicken in half almost but not all the way through; open like book. Brush with mustard; sprinkle with pepper and salt. Lay 1 prosciutto slice on each breast; fold breast over to enclose.
Place 1 sheet of phyllo on work surface, keeping remainder covered with damp towel to prevent drying out. Brush with butter; top with second sheet. Centre 1 breast on phyllo about 2 inches (5 cm) from short edge; fold edge over chicken. Fold sides over and roll up. Place, seam side down, on greased rimmed baking sheet; brush with butter. Repeat with remaining phyllo, butter and chicken. (Make-ahead: Cover with plastic wrap and refrigerate for up to 8 hours.) Bake in oven for about 45 minutes or until golden and chicken is no longer pink inside.
In large heatproof bowl or top of double boiler, whisk egg yolks until pale; whisk in stock and vermouth. Place over simmering water; whisk for about 8 minutes or until thickened and frothy. Whisk in parsley, basil, oregano, lemon juice, salt and pepper. Serve with chicken bundles.