• In a food processor, combine the white wine, vinegar, mustard, Worcestershire sauce and garlic or shallots; process until well blended.
• With the machine running, slowly pour the olive oil through the feed tube and process until well mixed.
• Add the rosemary and marjoram; process until herbs are finely chopped. Season to taste with salt and pepper. Set aside.
• Put the chicken breasts between sheets of waxed paper and pound until an even thickness (or butterfly and halve).
• Place chicken in a glass baking dish that will hold the breasts in one layer. Pour the marinade over the chicken, turning to coat. Cover and refrigerate at least 4 hours, up to 24 hours, turning occasionally.

Grilling Method

• Prepare a medium-hot fire in a charcoal grill or preheat a gas grill on high.
• Oil the grill racks.
• Remove chicken from the baking dish, reserving the marinade. Place chicken on grill and if using a gas grill, reduce all the burners to medium heat. Cook chicken, covered, 3 minutes or until seared.
• Brush with marinade. Turn over, brush with marinade again and grill 3 to 4 minutes until the other side is seared and an instant-read thermometer inserted into thickest portions registers 165 degrees.

Sous Vide + Grilling Method

• Remove chicken from marinade. Place in a single layer in sealable bags, or in zip top baggies and seal. If using zip top baggies, remove all the air from the bags (follow directions for your sous vide machine).
• Set your sous vide cooker to 145 degrees.
• Add sealed bags to the water and cook for 1½ to 4 hours.
• Around 10 to 15 minutes before you plan to take the chicken out of the water bath, preheat a grill to high.
• Remove breasts from bags. Oil grill grates. Grill chicken for 2 to 3 minutes per side, or until golden brown and nicely marked.