Chicken With Grape Mustard Cream Sauce

• 1 1/2 grapes seedles
• 1 grape cluster marjoram (fresh)
• 270 gr chicken (boneless skinless)
• 120 ml dry wine (white)
• 60 ml cream (heavy)
• 45 gr mushrooms (sliced)
• 28 gr butter
• 16 gr onion (minced)
• 16 ml dijon mustard
• 3 gr marjoram (crushed)