Chicken Kotletki With Sour Cream Sauce

• 1 filling
• 1 egg
• 220 gr bread crumbs (fresh)
• 160 ml whipping cream
• 160 ml sour cream
• 120 gr mushrooms (fresh)
• 120 ml cream (light)
• 55 gr butter
• 30 gr green onions (finely chopped)
• 16 ml oil