Trim ends off green beans.
Stem sage. Set aside four largest leaves and mince remaining leaves.
Pat chicken breasts dry and, on a separate cutting board, halve chicken lengthwise. Season both sides with a pinch of pepper.
Prepare the Chicken
Separate four slices of prosciutto (use remaining as you wish).
Place whole sage leaf on each slice and top with chicken piece.
Place open gallon bag on a clean workspace. Place two prosciutto-sage-chicken pieces in bag and gently pound with a heavy object until ¼"-thick.
Remove from bag and place on a plate, wrapping any hanging prosciutto over meat. Repeat with remaining two pieces. Refrigerate.
Cook the Green Beans
Bring a medium pot with ½ cup water to a boil over medium-high heat.
Add green beans and ½ tsp. salt, stir, and cover.
Stir occasionally until tender, 5-8 minutes.
While green beans cook, start chicken.
Cook the Chicken
Place a large non-stick pan over medium-high heat and add 1 Tbsp. olive oil.
Place chicken in hot pan, prosciutto side down, and cook until crispy and brown, 2-3 minutes.
Lower heat to medium. Flip chicken, and cook until chicken reaches a minimum internal temperature of 165 degrees, 3-5 minutes.
Remove to plate, tent with foil, and rest 3 minutes.
Reserve pan; no need to wipe clean.
Make the Sauce
Return pan used to cook chicken to medium-high heat and add 1 tsp. olive oil.
Add garlic and cook until aromatic, 30-90 seconds.
Add demi-glace, ¼ cup water, any accumulated juices from resting chicken, and minced sage. Bring to boil and cook until slightly reduced, 1-2 minutes.
Remove from burner and swirl in butter.
Plate dish as pictured on front of card, spooning sauce over green beans and chicken. Bon appétit!